HP15 0TH

October 3, 2009 3:40 PM

The British postcode system, one of the things which Britain arguably does better than anyone else, is 50 years old. The system divides the entire UK into alphanumeric postal districts organised in a hierarchy, with the first one or two letters denoting a postal area (typically a city or the environs of one, though London has several). Unlike systems elsewhere (such as the US, Australia, and most of Europe), it doesn't stop at the neighbourhood level, with each 5-to-7-character full postcode denoting a segment of a street. This makes it useful for applications other than addressing mail, such as navigation; as such, you can enter a postcode into Google Maps or a satellite navigation unit and be shown exactly where it refers to.

Unfortunately, though, the database of postcodes and their locations is another victim of the British institutional custom of copyrighting taxpayer-funded databases and licensing them only at great expense and under onerous terms (see also: the Ordnance Survey), effectively restricting them to moneyed corporations. However, there are several unofficial efforts to assemble this data from scratch and release it into the public domain.

posted by acb (126 comments total)

A few mates of mine were testing the post code system and its accuracy while I was at University by playing with the amount and accuracy of the information on the letter. One in particular was delighted to find that post would get to his house if he only put the house number and the post code on the front of the envelope.
posted by Brockles at 3:47 PM on October 3 [2 favorites]

The system itself sounds really cool. I wish more countries would just bite the bullet and use more efficient systems. For example, as a US citizen, I would love to see a reorganization of the postal system, switching to SI, and so on. It seems like if new systems were introduced slowly, over the course of years, while still supporting the old systems for a time, it wouldn't cause too much of a headache. It's always political will that is the problem, it seems.

Best of luck to the groups trying to get that into the public domain, where it belongs.
posted by metacollin at 3:54 PM on October 3

The Canadian postal code system has the same granularity, and as I just found out (inspired by your mention of it), is also on Google Maps. Our codes are a bit different, consisting of 3 letters and 3 numbers in a repeating pattern, so for example the postal code of GM Place in Vancouver (Canucks' home rink) is V6B 6G1. It also lets Canada Post give Santa a postal code of H0H0H0, so that scheme has that going for it.

And as an improvement on the British system, there's a free online lookup on Canada Post's site, plus anyone who wants the full directory can buy it on a CD or a download from Canada Post directly (more expensive) or from literally dozens of data resellers for as little as $100 including latitude and longitude coordinates for the post codes.
posted by barc0001 at 3:59 PM on October 3 [5 favorites]

Canada's Postal Code system is closely modelled on the UK's system. Individual postal codes generally have a granularity of half of a single city block (either odd or even).
posted by Mitheral at 3:59 PM on October 3

Unlike systems elsewhere (such as the US, Australia, and most of Europe), it doesn't stop at the neighbourhood level, with each 5-to-7-character full postcode denoting a segment of a street.

actually, the u s system has four additional digits which can identify city blocks or apartment buildings
posted by pyramid termite at 4:04 PM on October 3 [1 favorite]

pyramid termite: "actually, the u s system has four additional digits which can identify city blocks or apartment buildings"

But nobody bloody uses them.

An interesting twist in the post-code story: my old postcode (SN7) was in the county of Oxfordshire but in the postcode area around Swindon, in Wiltshire. Therefore the local Gas (British Gas, i.e. natural gas, not gasoline) offices were constantly passing our area between them, Wiltshire's saying we were in the wrong county and Oxfordshire's saying that we were in the wrong postcode. Neither accepted that we were in their service area and therefore ensuring that we couldn't get gas pipes laid and therefore no service.

(Note: it's been 10 years since this happened, I may be fuzzy on the details, but in essence: postcodes were another layer by which bureaucracy could faff around.)
posted by subbes at 4:13 PM on October 3 [1 favorite]

I read something about post codes appearing on wikileaks the other week. I don't fully understand how it can be funded by taxpayers' money, and then not be in the public domain.
posted by CitrusFreak12 at 4:14 PM on October 3

Only three houses share my Canadian postal code. Google Maps finds us.
Santa Claus has his own code, but for some reason Google can't find him:

SANTA CLAUS
NORTH POLE H0H 0H0
CANADA
posted by weapons-grade pandemonium at 4:15 PM on October 3 [1 favorite]

I think the UK's postal code for Santa (SAN TA1) beats Canada's any day.
posted by nmiell at 4:18 PM on October 3

actually, the u s system has four additional digits which can identify city blocks or apartment buildings

But nobody bloody uses them.

I use mine. Mail that I receive often also uses mine. Just because you don't use them doesn't mean nobody bloody does.
posted by Flunkie at 4:19 PM on October 3 [4 favorites]

Who managed to grab SAN TA0?
posted by Lemurrhea at 4:24 PM on October 3 [3 favorites]

And as an improvement on the British system, there's a free online lookup on Canada Post's site

There's a free online lookup on the Royal Mail website too, although you can only do 15 searches a day apparently.
posted by knapah at 4:28 PM on October 3

CitrusFreak12: "I don't fully understand how it can be funded by taxpayers' money, and then not be in the public domain."

I think the usual argument there would be that most volume requests for access to this sort of information is done by companies and not taxpayers, so by charging for this access they are actually deferring some of the operating costs of the postal system as a benefit to the same taxpayers/postal service users. In Canada, if you want to find postal codes one at a time you can do it for free either on Canada Post's website, or by going down to a post office and looking at the directory.
posted by barc0001 at 4:28 PM on October 3

Canadian codes alternate letters and numbers to minimize confusion between them, so we can't do the SANTA thing.
posted by weapons-grade pandemonium at 4:28 PM on October 3

I will often look up the zip+4 for an address if I'm going to be mailing to it more than once (my rent checks, for example). Commercial mail sent to me usually has it, presumably as a side effect of whatever bulk-mail discount stuff they're taking advantage of.

FWIW, the US post code system actually has two more digits, the delivery point code, which (along with the zip+4) is supposed to narrow things down to a single address, but I think the 11-digit zip+4+dp is only ever used in bulk-mail barcodes.
posted by hattifattener at 4:30 PM on October 3

I don't fully understand how it can be funded by taxpayers' money, and then not be in the public domain.

Quite simply the copyright is held by the institution creating the work, i.e. Royal Mail.

That's the how. As for the why - that boils down to a political decision. The argument used here (Denmark) for e.g. not letting the National Survey release their geodata for free is that is would create an unfair market for commercial geodata purveyors; the idea being that the state would be undercutting free initiative.
posted by brokkr at 4:30 PM on October 3

My ZIP + 4 is unique to my building only.
posted by ericb at 4:37 PM on October 3

One in particular was delighted to find that post would get to his house if he only put the house number and the post code on the front of the envelope.

This doesn't really seem much of a stretch - when I enter my delivery address to most websites this is all the information it needs to auto-fill the rest.

When I was a kid there were about 15 lines in my address... though admittedly the last half were probably United Kingdom, Europe, The World, The Milky Way...
posted by Acey at 4:41 PM on October 3 [2 favorites]

Brockles: that's a design feature. Each house number should appear in each postcode once. In theory, you only ever need a house number and a postcode to uniquely identify a property.

It works about 80-90% of the time, as anyone who's worked in a call centre will tell you.
posted by Leon at 4:51 PM on October 3

Pedantically speaking, we can't actually do SAN TA1 in the UK. The postcode normally comprises two letters followed by a number, and number followed by two letters e.g. WZ2 4GH. So I'm afraid RUD 0LF wouldn't get to the right address.....
posted by MajorDundee at 4:51 PM on October 3

Of course releasing the data undermines commercial efforts. That's a feature, not a bug. Why should taxpayers pay twice, especially for publicly useful information? Even in Denmark don't seem to understand that business interests are secondary to human interests?
posted by DU at 5:00 PM on October 3 [6 favorites]

Flunkie: "

actually, the u s system has four additional digits which can identify city blocks or apartment buildings

But nobody bloody uses them.

I use mine. Mail that I receive often also uses mine. Just because you don't use them doesn't mean nobody bloody does."

Yes, I misspoke there. I should have said - nobody that I know, or have a postal relationship with, knows their +4: they do, however, know their regular zip code like their own phone number. I'm not sure that I would be able to explain why they'd need to, for regular postal use; after all, mail gets there without the +4.
posted by subbes at 5:06 PM on October 3

As a resident of the US who often corresponds with the UK, I must say that I find a mixed alpha-numeric system confounding. When dealing with handwriting, I must distinguish between "I," ""J" and "1" and "7" and "F," for example.
posted by Morrigan at 5:09 PM on October 3 [1 favorite]

actually, the u s system has four additional digits which can identify city blocks or apartment buildings

I was under the impression that US ZIP+4 codes and Canadian postcodes weren't geographically contiguous.

Do mapping services or navigation devices accept them as coordinates? If not, is it for technical, legal or purely cultural reasons?
posted by acb at 5:32 PM on October 3

Pedantically speaking, we can't actually do SAN TA1 in the UK. The postcode normally comprises two letters followed by a number, and number followed by two letters e.g. WZ2 4GH. So I'm afraid RUD 0LF wouldn't get to the right address.....

You can't if it's treated as a regular postcode. Some postcodes don't match the letters-numbers-numbers-letters rule. These include codes for overseas territories (i.e., TDCU 1ZZ is the south Atlantic island of Tristan da Cunha) and the code GIR 0AA (which is used for Giro payments, which are, from what I understand, a type of financial transfer service people used before credit cards and PayPal).
posted by acb at 5:35 PM on October 3

This data set is available on wikileaks.
posted by futureproof at 5:39 PM on October 3

Morrigan, the standard UK postcode format is usually letter letter number gap number letter letter. Bearing this in mind will reduce confounding between 0 and O and 1 and I.
As an aside the Irish cabinet has only recently agreed to proceed with a postcode system. Not apparently for the benefit of An Post but for the emergency services and sat-nav.
posted by Dr.Pill at 5:41 PM on October 3 [1 favorite]

wikileaks link
posted by Rhomboid at 5:56 PM on October 3

I wonder what the Irish postcode system will look like. Will they go for a continental-style numeric system, for similarity with the Eurozone and to avoid anything that resembles colonial deference, a British-style alphanumeric system, or something entirely new? If the impetus came from navigation rather than the post, I imagine it'll have more precision than ZIP codes or continental postcodes, though if it's all numeric, those could get quite long.
posted by acb at 6:06 PM on October 3

One fun thing about US zip-codes is that the post office completely ignores "City, State" part of an address. I have a friend who has all of his mail addressed to "Allegheny City, PA", a city that hasn't existed since 1907. As long as the zip is 15233, the post office delivers the mail without a problem.
posted by octothorpe at 6:09 PM on October 3

But nobody bloody uses them

Except for almost every business or agency that sends you mail of any sort at all, and almost any business or agency that you return mail to.

But apart from every business and agency you deal with, nobody at all.

Which is fine, since that finer detail is mostly of use to businesses trying to cut costs by using less than first-class postage.

I was under the impression that US ZIP+4 codes and Canadian postcodes weren't geographically contiguous.

They aren't required to be, and IIRC they represent groups of routes rather than areas. Mostly they are though. But it is possible that a given block might be one zip+4 on one side and a different one on the other if the two streets the block is between are on different routes.

Do mapping services or navigation devices accept them as coordinates?

Google maps accepts zip, but seems to ignore the +4.. I think it returns the centroid of the zip code tabulation area, which is a different beast created by the Census.
posted by ROU_Xenophobe at 6:31 PM on October 3

Interestingly, I'm pretty damn sure I saw a pirate copy of the UK postal codes being hawked on...? Reddit programming? Grab the torrent instead of paying $1700ish to the goobermint for what is probably rightfully regarded as public property.

It's a big mistake to let the government privatize data services.
posted by five fresh fish at 6:32 PM on October 3

> I think the UK's postal code for Santa (SAN TA1) beats Canada's any day.
posted by nmiell at 7:18 PM on October 3 [+] [!]

Apparently a reindeer crapped coal on your head as a child.
posted by Decimask at 6:35 PM on October 3 [1 favorite]

Brockles: that's a design feature. Each house number should appear in each postcode once. In theory, you only ever need a house number and a postcode to uniquely identify a property.

It works about 80-90% of the time, as anyone who's worked in a call centre will tell you.

I used to do mailshots and the Royal Mail guarantee the delivery of a letter so long as it has the first three characters of the address line and the postcode. That's all they ever need, supposedly.


As an aside the Irish cabinet has only recently agreed to proceed with a postcode system. Not apparently for the benefit of An Post but for the emergency services and sat-nav.

I remember taking the address of somebody who lived in Donegal. He had to assure me that not only did postcodes not exist there, but I didn't even need his address line. I kid you not.
posted by Sova at 6:35 PM on October 3

Grab the torrent instead of paying $1700ish to the goobermint for what is probably rightfully regarded as public property.

Except that you can't use it publicly, because if you do, the government can and will sue you and from what I understand, they have a pretty solid case. (Disclaimer: IANAL)

Unlike the US, Britain has a legal concept known as "Crown Copyright", which lets the state assert copyright on things belonging to it. The state in Britain is not notionally the people (as in a republic) but the monarch (hence the word "crown"), and grubby little schemes like this are one of the surviving vestiges of the aristocratic system.
posted by acb at 6:50 PM on October 3 [3 favorites]

I used to do mailshots and the Royal Mail guarantee the delivery of a letter so long as it has the first three characters of the address line and the postcode. That's all they ever need, supposedly.

Doesn't work with people who insist on calling their house "The Larches" instead of "49". Bastards.

I wonder what the Irish postcode system will look like.

I'd like to see a Hilbert Curve covering the entire planet. Then a location can be assigned a number with arbitary precision, and knocking off the least-significant-digits gives you a larger and larger area. I admit the numbers may end up a bit unwieldy.
posted by Leon at 6:53 PM on October 3 [3 favorites]

Morrigan, the standard UK postcode format is usually letter letter number gap number letter letter. Bearing this in mind will reduce confounding between 0 and O and 1 and I.

It's a bit more complex than that. The first part (the "outcode") is always one or two letters representing the post town (only big cities get one letter), followed by one or two digits representing the subdivision of the town, or if it's a central London postcode one digit and one letter, since the numerical subdivisions were made far too big. Call centre operatives have no idea about this last part.

The second part (the "incode") is always number letter letter as far as I know.
posted by cillit bang at 6:58 PM on October 3

Who actually mails things anymore?
posted by crossoverman at 7:00 PM on October 3

Amazon.
posted by Leon at 7:05 PM on October 3 [2 favorites]

Wouldn't happen in the states. Wouldn't want to give the terrirsts access to the exact address of the white house or shea stadium with geosync coordinates.
posted by Severian at 7:07 PM on October 3

I remember taking the address of somebody who lived in Donegal. He had to assure me that not only did postcodes not exist there, but I didn't even need his address line. I kid you not.

Allegedly, someone once wrote an angry letter to Pat Spillane (famous/controversial Gaelic footballer/commentator) addressed simply "Pat Spillane, The Bollix, Kerry" and it reached its destination.

I've seen evidence of this in Waterford - post where every line of the address is wrong, or addressed to houses we haven't lived in in 20 years all turns up in the letterbox without fail. It helps to be on first name terms with the postman though.

To me, the main benefit of the introduction of postcodes will be that I don't have to make up stuff for those damn websites that require them.
posted by kersplunk at 8:02 PM on October 3

The zip+4 that we use in the United States is actually a citizen relocation code. Hopefully we'll never need to use them.
posted by pjdoland at 8:02 PM on October 3 [1 favorite]

Wouldn't want to give the terrirsts access to the exact address of the white house or shea stadium with geosync coordinates.

You joke, but I've had transit agency employees say they cannot divulge schedule information or route information in electronic format for security reasons - it would be bad for people to know where buses stop. Thankfully, most of those people are coming around.
posted by GuyZero at 8:03 PM on October 3

CitrusFreak12: "I don't fully understand how it can be funded by taxpayers' money, and then not be in the public domain."

That federal government creations are in the public domain is one of the things America does better than almost anyone else. Wikipedia, in particular, has worked laboriously to persuade certain countries to allow their works to be used within the project. 99% of the time, it is only possible to include a fair use version (e.g. degraded resolution). It's not even true of most works of US state governments.

This includes, pace the monarchy-crown distinction raised by acb, most of the world's republics.
posted by dhartung at 8:07 PM on October 3 [4 favorites]

There's a mildly annoying quirk of using Canadian postal codes on a keyboard.

Because the codes are an alternating sequence of capital-letter, number, capital-letter, they can be slow to type. SHIFT+Letter, number, SHIFT+Letter, number, space... etc.

I always used to need two tries at my old postal code, M4R 2E9, after invariably typing M$R 2E9.
posted by generichuman at 8:32 PM on October 3 [1 favorite]

There are two mildly annoying quirks about Canadian postal codes. One is the misplacing of shift (on the rare occasion I think to use caps lock I immediately forget and then end up with h$c @l*) and the second is the inconsistency in whether input forms require or do not allow the space.
posted by jeather at 8:46 PM on October 3

Wouldn't want to give the terrirsts access to the exact address of…shea stadium with geosync coordinates.

I hate to break it to you, but…
posted by oaf at 8:56 PM on October 3

My (Canadian) postal code is V6G 1H7. I here issue a challenge to enterprising MeFites to show my where I live.
posted by Turtles all the way down at 9:01 PM on October 3

show me //for Christ's sake
posted by Turtles all the way down at 9:02 PM on October 3

Haro Street at Gilford? It's a 2 second google followed by a click through google maps, as are all Cdn postal codes.
posted by Durn Bronzefist at 9:24 PM on October 3

So it is. I hope I'll be forgiven if I expected the postal code "V6G 1H7" to link to porn with captions in l33t5p37k.
posted by ROU_Xenophobe at 9:34 PM on October 3

"The argument used here (Denmark) for e.g. not letting the National Survey release their geodata for free is that is would create an unfair market for commercial geodata purveyors; the idea being that the state would be undercutting free initiative."

This is the case with Crown created data in BC too. The case I'm familiar with is map data used for Forestry. It's an interesting kick in the teeth for environmental groups because Forestry companies get to deduct the cost of obtaining electronic map sheets from the stumpage they pay for cutting trees on crown land. Environmental groups though are forced to absorb the cost. And it isn't cheap, to buy the whole province was over a million dollars 15 years ago. Like dhartung said it's one place the US gets it right over Canada.

Worse though, and the US gets this wrong too, is you are required to buy building codes. Literally the law of the land and you have to pay to gain access.

"To me, the main benefit of the introduction of postcodes will be that I don't have to make up stuff for those damn websites that require them."

Isn't there a handy popular TV show whose title is a postal code? 90210 is my go to zip code.
posted by Mitheral at 9:37 PM on October 3 [1 favorite]

"Haro Street at Gilford? It's a 2 second google followed by a click through google maps, as are all Cdn postal codes."

Specifically Canada Post will tell any one that V6G 1H7 is the BUCHAN HOTEL at 1906 HARO ST
posted by Mitheral at 9:39 PM on October 3

Who actually mails things anymore?

Those of us who don't feel like emailing DVD sized chunks of data?
posted by rodgerd at 9:52 PM on October 3

When I was a kid there were about 15 lines in my address... though admittedly the last half were probably United Kingdom, Europe, The World, The Milky Way...


UK addresses always baffled me.
They're always like:

4 Oxfordshire 5M
Wormsley-on-Thames
Cheeseworthshireford
Sussex, England
United Kingdom
W1

Whereas mine were always, "3 Main St., Toronto, Ontario."
posted by chococat at 9:58 PM on October 3 [3 favorites]

V6G 1H7...

If you compare the above with V6G 1H5 and V6G 1H3 in Google Maps, you'll see that is a very dense area.
posted by rokusan at 10:03 PM on October 3

And US, UK and Canadian addresses are all a joke. If you want fun, you need to get deep into old-school Tokyo addresses. Not only might building #4 be on a block in between building #125 and #17, but the full addresses translate like this...

 The Red House with the Windows
 Around the Corner Left of the Building That Used to be the Bank
 Neighborhood's Unofficial Nickname
 Alternate Name for District (Which You Have Never Heard Before)
 A Ward or Prefecture You Probably Know
 Japan

Following an address might get you within a few miles, but after that you'd better know where you're going. A few months of dealing with those and you understand why everyone in Tokyo draws a map for everything.

They might as well just use haiku.
posted by rokusan at 10:08 PM on October 3 [3 favorites]

turtles all the way down, we're neighbors!
posted by stray at 11:44 PM on October 3

Years ago I got lumbered with doing tech support for a site I'd been involved in building. A steady stream of angry people got in touch claiming the site wouldn't accept their perfectly valid postcodes, and it always turned out they'd confused O with 0, something they'd probably done for many years without realising. But when I politely pointed this out, complete with link to the Royal Mail postcode finder, I usually got irate replies along the lines of "How dare you tell me I don't know where I live!!".
I've carefully avoided tech support duties ever since.
posted by malevolent at 1:08 AM on October 4

Specifically Canada Post will tell any one that V6G 1H7 is the BUCHAN HOTEL at 1906 HARO ST

Well, touché, but CP almost always gives you a range of addresses, not a single building, as appropriate for the code. Actually, I think mapquest did, too. I don't know why google maps won't spit out the addresses.
posted by Durn Bronzefist at 1:17 AM on October 4

It always turned out they'd confused O with 0

The national tendency to always pronounce nought as 'oh' in the context of phone numbers and postcodes probably wasn't helping.
posted by the latin mouse at 1:45 AM on October 4

Indeed, what's the origin of that?
posted by A189Nut at 1:52 AM on October 4

I'm not sure if this is still the case, but certainly in the past employees of the Royal Mail had to sign the Official Secrets Act because the mail was that important. It may be that sort of mindset that's part of the 'not telling anyone all the postcodes'.

I remember taking the address of somebody who lived in Donegal. He had to assure me that not only did postcodes not exist there, but I didn't even need his address line. I kid you not.

You can get away with this in rural Scotland too; name, village, county will get it there, albeit covered with warnings from the PO about playing silly buggers with addresses. My mum also has had a letter delivered when she couldn't remember the address but could remember where it was, so drew a map on the envelope.

The Orkney islands and Caithness have 'KY' as their postcode prefix, which is always good for an immature giggle. It also illustrates that when you get really rural the initial postcode prefix can cover a huge geographical area, that's not necessarily even on the same island. This is fine, except when delivery computers are postcode based, and programmed by people who've never been north of Watford - so the delivery guys are told that they can do X amount of deliveries in a morning, when that would involve their van breaking the sound barrier...
posted by Coobeastie at 2:13 AM on October 4

Bollocks. KY is Fife, not Orkney/Shetland.
posted by the cuban at 3:11 AM on October 4

The British postcode system, one of the things which Britain arguably does better than anyone else...

OK, I'll argue with that. This is a system that doesn't allow you to check, in a relatively straightforward way, whether something is a valid postcode. The second block is (as far as I know) always a numeral followed by two letters. But the first block is one or two letters, followed by one or two numerals, and sometimes followed by another letter. And not all such combinations are valid. Wikipedia has the gory details, and they say that "completely accurate validation is only possible by attempting to deliver mail to the address". That's a lot more complicated than the US and most of Europe (where you just check that you have the right number of numerals) or Canada (where you check for the letter-numeral-letter, numeral-letter-numeral pattern).
posted by klausness at 3:39 AM on October 4

Richard Whitely, former presenter of Countdown, got fan mail delivered to him that was addressed to:

Dick,
England
posted by knapah at 3:44 AM on October 4 [1 favorite]

And a friend of mine was proud that a letter addressed to

B**** [his family name]
Masham
England

would reach him from anywhere in the world. We tried it from several locations. It did.
posted by aqsakal at 4:08 AM on October 4

Bollocks. KY is Fife, not Orkney/Shetland.

You're right the_cuban, sorry. Orkney is KW, close enough for me to be confused!
posted by Coobeastie at 4:13 AM on October 4

The British postcode system, one of the things which Britain arguably does better than anyone else...

I had hesitated, because the huge majority of comment seemed to agree with this. But now (timidly, as only my second MeFi post) I would argue, too. First problem: you need to know somebody's postcode in advance in order to write to them. This is fine when you are replying to someone who has quoted their postcode, but not when sending a "cold call" mail.

Secondly, let's not forget there are millions of old folk out there with no access to internet, nor any idea of what it is or how to use it. I worked for years in the department of a UK Embassy which handled all incoming queries from the public, and postcode info was a VFAQ. We had to maintain and keep updated (at taxpayer's expense) a shelfful of UK postcode directories almost two metres long, and an employee spent many workhours looking up postcodes for "punters" from the public. Mammas who could not transfer money to their kids studying in the UK because they did not have, or had transcribed incorrectly, their postcode, customer enquiries to UK companies, etc. Even now, telling enquirers they can look it up on internet provokes a an astounded and usually angry response.

Thirdly, this system doesn't allow a "generic" code when you haven't got access to the correct one, in order to arrive at least close enough to the destination for manual processing. My postcode in Rome used to be 00135 - using 00100 a sender could get close enough for the mail to arrive with a day's delay.

I was working in the then West Germany shortly after the UK intoduced their system. The German, French, etc. (numerical) systems were already in place (the German since 1941, according to Wikipedia!) and successful. I couldn't believe that a public servant could be allowed to propose something as clunky as the UK system apparently without having looked around first at what was already working well elsewhere.
posted by aqsakal at 4:31 AM on October 4 [1 favorite]

Wikipedia has the gory details, and they say that "completely accurate validation is only possible by attempting to deliver mail to the address". That's a lot more complicated than the US and most of Europe (where you just check that you have the right number of numerals) or Canada (where you check for the letter-numeral-letter, numeral-letter-numeral pattern).


Are you saying that every \w\d\w\d\w\d combination maps to an existing Canadian postcode? Or, indeed, that every combination of five digits is a US ZIP code?
posted by acb at 4:35 AM on October 4

I was working in the then West Germany shortly after the UK intoduced their system. The German, French, etc. (numerical) systems were already in place (the German since 1941, according to Wikipedia!) and successful.

What's the size of an area denoted by a German or French postcode? About the same as a US ZIP code or the first half of a UK postcode, I'm guessing. Which makes it useless for navigation.
posted by acb at 4:37 AM on October 4

What's the size of an area denoted by a German or French postcode? About the same as a US ZIP code or the first half of a UK postcode, I'm guessing.

Relative to the size of the country, you're probably correct. Germany is about 3.6% as big as the U.S., 4.4% if you exclude Alaska. Its postal codes should be at least 22 times more precise than those in the U.S.
posted by oaf at 4:49 AM on October 4

acb: This should give an overview: http://www.webmap.de/plz.html

[Sorry, still trying to work out how to post a link.]
posted by aqsakal at 4:53 AM on October 4

Who actually mails things anymore?

I always tell people to send me physical things by email as attachments. The pause while they work out whether this is possible or not is a moment of great mechanical wheel turning beauty and highlights a cultural acceptance of the possibility of technological magic.
posted by srboisvert at 5:00 AM on October 4 [5 favorites]

Thirdly, this system doesn't allow a "generic" code when you haven't got access to the correct one, in order to arrive at least close enough to the destination for manual processing. My postcode in Rome used to be 00135 - using 00100 a sender could get close enough for the mail to arrive with a day's delay.

You say generic, but your answer looks like a partial and you can send mail in Britain using only the first part of the postcode. The Liver Building is L3 1HT, but marking the envelope L3 will get it as far as the Liverpool docklands, even if the postman will need to read the rest of the envelope to find which building is intended.

Similarly you can send mail in the UK without a postcode at all. Including the code just makes it easier on the post office.
posted by the latin mouse at 5:07 AM on October 4 [1 favorite]

I have a NY address that I have mailed two different postcards to from overseas with only this scribbled on them:

  nnn nnth
  100nn

(Yes, I was drunk. But it worked.)
posted by rokusan at 5:36 AM on October 4

chococat - its spelt Cheeseworthshireford, but its pronounced Chey-wuth-she-fo.
posted by Jofus at 5:54 AM on October 4 [1 favorite]

its spelt Cheeseworthshireford, but its pronounced Chey-wuth-she-fo.

It'd probably be pronounced "Chefferd."
posted by rokusan at 6:22 AM on October 4 [4 favorites]

Try the Nicaraguan address system sometime. It's based on landmarks -- both current and no-longer-existing [1] [2] -- and directions. People use the system even if their streets have names and house numbers. To make things more complicated, they substitute east-west-north-south with up-down-(cityspecific). And instead of using meters or feet or yards, they use varas. To make things even more complicated, they often use abbreviations, especially on billboards. I found a good write-up of the system. There's a quiz.

[1] A lot of landmarks moved after the 1972 earthquake.

[2] There's a restaurant called El Arbolito (The Little Tree). When you get an address that starts with "from where the little tree used to be..."
posted by bentley at 6:29 AM on October 4

the zip+4 system in the US is actually pretty granular.

my favorite wtf addressing thing is the seattle area, where e.g. "west 140th" is COMPLETELY DIFFERENT than "140th west". took me a while to figure that out after i moved there.
posted by rmd1023 at 6:45 AM on October 4

In Canada, I have had mail delivered accurately and promptly with the envelope bearing just a first name, wrong house number, wrong street name, correct town and province and correct postal code. I always get mail from my mummy despite the fact that she doesn't know my name (she still doesn't get that I didn't hyphenate my family name after marriage) or my street address but she does have the right postal code. I've mailed things with just a name and postal code that have gotten to their destinations. Canada post rocks.

And yeah, when I lived in Donegal I couldn't understand my own address (especially because half would be gaelic and half english and sometimes it would switch). The nice think in Tokyo though is that outside all the tube stops there is a map of the neighbourhood with all the blocks given the "neighbourhood" name.
posted by saucysault at 7:22 AM on October 4

acb : The British postcode system, one of the things which Britain arguably does better than anyone else

FTA: "As the format of the codes does not achieve its objective of primarily identifying the main sorting office and sub-office they have been supplemented by a newer system of five-digit codes called Mailsort"

I don't know if I'd describe "failing in its primary function" as doing it "better". :)


Brockles : One in particular was delighted to find that post would get to his house if he only put the house number and the post code on the front of the envelope.

This works in the US, as well (even with just the five-digit zipcode rather than all nine) - I usually only put a street address and zipcode on my mail, unless the recipients themselves need more information (ie, "Attn: Customer Service").


subbes : But nobody bloody uses them.

I do. And it does help, too - For about three years, I couldn't convince the electric company that they had my street name totally wrong (I know, right? Bet they'd still have found me in a heartbeat to disconnect me if I didn't pay), but because I had given them the full 9-digit zipcode, I never had my mail go to the wrong place.


brokkr : the idea being that the state would be undercutting free initiative.

That only makes sense if the state did it deliberately to compete. If the government decides it needs to know something and uses taxpayer money to collect that data, they'd damned well better release it to the people who paid for it. If that overlaps a service the private sector provides, TFB.
posted by pla at 7:27 AM on October 4

rather than using the (large) leaked file listed above, to get lists of nearby postcodes i use
Natural England
a site with a reasonably good interface that (somewhat incidentally) lets you enter partial postcodes and it lists postcodes in the next lower level of granularity.
posted by dongolier at 7:29 AM on October 4

~Fondly recalls a time when one need only address a letter with the recipient's name and the word "city" and it would get to them as long as it was mailed somewhere in the intended city.
posted by Thorzdad at 7:40 AM on October 4

Postcodes: best of the pre-net snail mail system.
posted by PeterMcDermott at 7:40 AM on October 4

pjdoland: "The zip+4 that we use in the United States is actually a citizen relocation code. Hopefully we'll never need to use them." This is a joke from the Simpsons, not a fact.
posted by gregr at 8:05 AM on October 4

I think a big part of the reason that UK addresses are so strange-looking to people who are used to the super-logical number,street,city,state format is because it really doesn't matter what you put, so long as you put the house number and the postcode correctly.
I am free to put my village name, the name of one or more nearby towns, this county or the next etc, or not. So long as it starts with 44 and ends with my postcode it'll be fine.
I recently got a postcard from my sister which had even less correct information (just correct spelling of my name, wrong house number, wrong county, and the postcode with one letter wrong!) I ought to frame it!
posted by mjg123 at 8:43 AM on October 4

acb: Unlike the US, Britain has a legal concept known as "Crown Copyright", which lets the state assert copyright on things belonging to it. The state in Britain is not notionally the people (as in a republic) but the monarch (hence the word "crown"), and grubby little schemes like this are one of the surviving vestiges of the aristocratic system.

Excuse me, but this is bullshit. The concept of 'Crown Copyright' did not exist before the Copyright Act of 1911. It has nothing to do with ancient monarchical privilege, and everything to do with the development of the modern bureaucratic state.

Your indignation would be better directed at the creeping privatisation of the Post Office, which means that the postcode database, rather than being crown copyright and managed (notionally at least) by the government on behalf of the public, is the property of 'Royal Mail Group Ltd' and managed as a commercial asset. The Post Office currently makes a profit of £1.5m a year from licensing the use of postcode data, and this figure is likely to increase if the organisation is sold off to the private sector and starts 'sweating the assets' to increase profitability.

To describe the postcode system as 'one of the things which Britain arguably does better than anyone else' brings on a nice warm patriotic glow, but the fact is that the entire British postal system is in crisis. See this article by a postal worker (writing under the pseudonym 'Roy Mayall' .. boom boom!) for a first-hand account of why the Post Office is in such a mess.
posted by verstegan at 9:14 AM on October 4 [4 favorites]

Just another tiny addressing anecdote - I used to live on a street called Dow Court in Madison, WI. At least once I got mail addressed to me, at (address number) Tao Court.

I often wondered if this would have worked in a place where the mail carriers were less likely to have advanced liberal arts degrees.
posted by hap_hazard at 9:29 AM on October 4 [2 favorites]

I think a big part of the reason that UK addresses are so strange-looking to people who are used to the super-logical number,street,city,state format is because it really doesn't matter what you put, so long as you put the house number and the postcode correctly.

No, I think it's just that people in the UK are more likely to use more parts of an address than in, say, the US.

I mean, in the US the things that are probably necessary to reliably get mail to me are either name, house + street, and zip, or even just name and zip+4.

You could probably get mail to me at:

ROU_Xenophobe
That House With The Mostly Brick Facade And The Little Gothic Cutout In The Pillar
Somewhere Near Those Two New Roundabouts
Western New York
Did You Know That Wallabies Are Marsupials?
My Cat's Breath Smells Like Cat Food
14226-XXXX
posted by ROU_Xenophobe at 10:23 AM on October 4

Excuse me, but this is bullshit. The concept of 'Crown Copyright' did not exist before the Copyright Act of 1911. It has nothing to do with ancient monarchical privilege, and everything to do with the development of the modern bureaucratic state.

Still, the predominant legal fictions of Britain (i.e., that of the monarchy, as opposed to those of republics, which have to do with the state being answerable to the people) allowed them to pull this off. Even in the US (a country which isn't exactly anti-corporate), the idea of citizens being denied access to the data their taxes paid for wouldn't be accepted quite so meekly. The traditions going back to the monarchy/aristocracy have made their mark on the social contract and civil institutions of Britain, and the people are still, in some ways, inclined to know their place and not make a fuss.

See this article by a postal worker (writing under the pseudonym 'Roy Mayall' .. boom boom!) for a first-hand account of why the Post Office is in such a mess.

I've read it, and it is worrying. Though it has little to do with the design of the postcode system, which I still contend is remarkably elegant.
posted by acb at 10:49 AM on October 4

There are many ways to pay for services provided by the state. Direct taxation of income is just one. Other successful mechanisms include, for example, the BBC television licence, requiring developers to provide public amenities as part of their planning applications, and requiring employers to subsidise socially-beneficial activities such as childcare and part-time working.

A national postage system that delivers mail according to statehood rather than economics (a letter from London to London costs as much as London to the Orkneys) is a service provided by the state. One way to pay for it we've devised is to license the postcode data.

You can make the case that the postcode data should be free to encourage other economic activities, but this is an economic, not a moral case. I do not see that just because the state creates a data set it must be free for use, though I concede this is a good starting-point.
posted by alasdair at 11:06 AM on October 4

Are you saying that every \w\d\w\d\w\d combination maps to an existing Canadian postcode? Or, indeed, that every combination of five digits is a US ZIP code?

No. You'd expect some postal codes to be unassigned, to allow for future expansion. But in every other country that I know of, the postal codes have a simple pattern that make it easy to verify whether a given sequence of numbers and letters is at least potentially valid. Before I read the wikipedia article, I thought I knew what valid UK postal codes looked like, and I would have guessed that something like EC1A 1BB (or anything starting with EC1A) couldn't possibly be a legitimate postal code, but apparently it is. On the other hand, NE1A 1BB wouldn't be valid (since no postal code starting with NE1A is valid, though postal codes starting with NE11 are valid), but how are you supposed to know that?

To put it another way, you know that 923875 could never be a valid US ZIP code, since it has six digits. But could E12B 4RT be a valid UK postal code? According to the wikipedia article, it wouldn't currently be, but there's no way of knowing whether it might be in the future (or whether the wikipedia article is wrong and it this is in fact a valid postal code).
posted by klausness at 11:12 AM on October 4

A national postage system that delivers mail according to statehood rather than economics (a letter from London to London costs as much as London to the Orkneys) is a service provided by the state. One way to pay for it we've devised is to license the postcode data.

I dislike such arguments because they're based on the implicit assumption that the ordinary person is a passive consumer rather than an active participant, and would benefit more from (a) the data being restrictively licensed and used to subsidise their consumption than (b) being freely available for them to use in their activity. Now it may be so that the majority of people are passive consumers most of the time (as per the 90-9-1 rule often cited), but once you enshrine this in policy, it serves to encourage passivity and discourage initiative. (Of course, there are concerns which profit from people being passive, usually those who wish to sell them things they would otherwise do themselves.) It would be far healthier for a society in my opinion to give people the benefit of the doubt, assuming that they're participants, or might choose to become such.

You can make the case that the postcode data should be free to encourage other economic activities, but this is an economic, not a moral case. I do not see that just because the state creates a data set it must be free for use, though I concede this is a good starting-point.

Why stop there? Why, for instance, should it be possible for an organisation to claim copyright on a collection of facts (as opposed to, say, a creative work)? There is no database copyright in the United States, and this hasn't stifled innovation there (quite the opposite, in fact).
posted by acb at 11:17 AM on October 4 [1 favorite]

I dislike such arguments because they're based on the implicit assumption that the ordinary person is a passive consumer rather than an active participant, and would benefit more from (a) the data being restrictively licensed and used to subsidise their consumption than (b) being freely available for them to use in their activity.

Historically that was the case - abundant computing power is a fairly recent innovation.

There is no database copyright in the United States, and this hasn't stifled innovation there (quite the opposite, in fact).

World leading telemarketing and spamming is not the innovation I wish to be exposed to.
posted by rodgerd at 11:43 AM on October 4

But in every other country that I know of, the postal codes have a simple pattern that make it easy to verify whether a given sequence of numbers and letters is at least potentially valid

All extant geographic UK postcodes follow the pattern [A-Z]([A-Z]?)([1-9]?)[0-9]([A-Z]?) [0-9][A-Z][A-Z]. The UK post office issuing a code outside this framework should be considered as likely a possibility as that of the USPS issuing a place with a 6 digit zip code.
posted by cillit bang at 11:55 AM on October 4 [1 favorite]

One thing thats particularly mad about the postcode being copyright is that some of the biggest users are public sector organisations. Every local council and NHS hospital is paying (significant sums) for postcode data.
posted by Lanark at 2:36 PM on October 4

My US Postal Service Post Office Box here in Berkeley has a unique 9-digit zip code. I tried sending a postcard cross-country addressed with only the digits; it arrived.

While this might be true for PO Boxes in other small cities, I'd be surprised if it were true for, say, New York City.
posted by Zed at 2:49 PM on October 4

I dislike such arguments because they're based on the implicit assumption that the ordinary person is a passive consumer rather than an active participant

Again, your general principles are good, but there are good pragmatic and historical reasons for having a less lofty attitude to the funding of public services. "Ain't broke, don't fix it" and all that. System works pretty well, no? Delivers a reliable, up-to-date and available infrastructure at reasonable cost? Sounds good to me. Maybe not to people who want to gain personal benefit from free access to this data, but if they get their way the Royal Mail will have to be compensated from my taxes, which I'd rather go to schools/hospitals/soldiers etc.

(Also, I don't quite get how "here, citizen, is some data" is active while"you want this? Come up with a business plan on how you're going to provide a marketable service to people with it...." is passive - but that's beside the point.)
posted by alasdair at 2:52 PM on October 4 [1 favorite]

Sounds good to me. Maybe not to people who want to gain personal benefit from free access to this data, but if they get their way the Royal Mail will have to be compensated from my taxes, which I'd rather go to schools/hospitals/soldiers etc.

You're still thinking about postcodes as something that naturally belongs to the Post Office. That may have historically been the case, though these days, the general public has at least as much of an interest in the postcode system (or, to describe it more accurately, a street coordinate system) as the Post Office does. Allowing the PO to charge monopoly rent on it is as beneficial to the public as allowing, say, O2 to have a monopoly on mobile phone service.
posted by acb at 3:59 PM on October 4

(Also, I don't quite get how "here, citizen, is some data" is active while"you want this? Come up with a business plan on how you're going to provide a marketable service to people with it...." is passive - but that's beside the point.)

Why should it only be available to those who can make a profit off it? Firstly, this pointedly excludes non-profit users, and put an additional financial burden on entities like councils, which are passed on to the taxpayer. Secondly, it is quite likely that, were postcode data opened up, the resulting economic benefits would outweigh the expense of doing so.

(A parallel is the GPS system, which costs a lot of money to maintain. The US Government could have just as easily kept the whole system encrypted and sold subscriptions to it, but if it did that, it would have slowed down adoption of GPS-based technologies and the related efficiency improvements that they enabled.)
posted by acb at 4:27 PM on October 4

in every other country that I know of, the postal codes have a simple pattern that make it easy to verify whether a given sequence of numbers and letters is at least potentially valid.

Of what possible benefit is that? If you're trying to fake an address for a form, you could just look up a real one.

If you're trying to get something to someone in particular, it matters that you have the one correct address, not a valid one in terms of it being something the post office can process and deliver... somewhere. How is this any different from not knowing if you can address something to 938 Boulder Street, Saskatoon, when Boulder St. only goes to 650?
posted by Durn Bronzefist at 4:35 PM on October 4

The US post office is no slouch either. Supposedly a letter addressed to:

HILL
JOHN
MASS


Was successfully delivered to John Underhill, Andover Massachusetts.
posted by splatta at 4:59 PM on October 4 [1 favorite]

The British postcode system, one of the things which Britain arguably does better than anyone else, is 50 years old.

The American postcode system is more than ten years older, covers a vastly wider spectrum of construction & population density, and doesn't have the proprietary Crown ownership bullshit.

I'd say you need to put down the crack pipe.
posted by Civil_Disobedient at 5:38 PM on October 4

The American postcode system is more than ten years older, covers a vastly wider spectrum of construction & population density, and doesn't have the proprietary Crown ownership bullshit.

It's also more coarsely grained, making it useless for routing. (Yes, you have ZIP+4, but that's not guaranteed to be geographically contiguous, and is not used for routing; Google Maps won't point to a block from a ZIP+4, and I doubt a satnav unit will do anything useful with one either.) Also, the British system's alphanumeric nature is more efficient, requiring fewer characters to represent information, and giving more information at a glance to human users. (I.e., one can guess, correctly, that OX4 is somewhere near Oxford, whereas a ZIP like, say, 15614 doesn't say anything to someone who hasn't encountered it before.)
posted by acb at 5:47 PM on October 4

Whereas a ZIP like, say, 15614 doesn't say anything to someone who hasn't encountered it before.

While I agree the UK or Canadian style codes are more useful, the US's zips aren't quite meaningless.

Since they're numbered from East to West, and in the approximate order that the nation was settled, you can tell that 15614 is in the Northeast, but not NY or Washington since those are 10's and 20's... so probably somewhere close to Cleveland or... Pittsburgh, as it turns out. And you'll remember 15--- is near Pittsburgh from now on, I'm sure.

Granted, not as much info as the OX3's, but it's more than nothing.
posted by rokusan at 12:50 AM on October 5 [1 favorite]

Huh. So that's where it is...
posted by You Can't Tip a Buick at 5:52 AM on October 5 [2 favorites]

Huh. So that's where it is...

Notice that if you zoom in on that map, there's a little guy in a canoe.
posted by rokusan at 6:04 AM on October 5 [2 favorites]

It's weird what people can get patriotic about.
posted by Summer at 6:35 AM on October 5

Allowing the PO to charge monopoly rent on it is as beneficial to the public as allowing, say, O2 to have a monopoly on mobile phone service.

Would giving O2 a monopoly on mobile phones help to give us all flat-fee calls for vastly less than they cost to carry? I'm all in favour, in that case.
posted by fightorflight at 7:52 AM on October 5

Google Maps won't point to a block from a ZIP+4

The test of whether something is useful is whether Google uses it?

Google Maps also doesn't display county boundaries (at least in the US), so I guess the division of states into counties is useless too.
posted by DevilsAdvocate at 10:45 AM on October 5

The test of whether something is useful is whether Google uses it?

No, but it is a good test of whether something is useful for finding destinations on a map (i.e., Google Maps' stock in trade). If it were practical to use ZIP codes for finding a segment of a street within short walking distance, Google would have presumably done so.

Google Maps also doesn't display county boundaries (at least in the US), so I guess the division of states into counties is useless too.
Straw man. That's not what Google Maps does; Google Earth might be able to do this, though.
posted by acb at 10:49 AM on October 5

Would giving O2 a monopoly on mobile phones help to give us all flat-fee calls for vastly less than they cost to carry? I'm all in favour, in that case.

Even if it inflated your council tax, bus fares, utility rates and other services whose providers the monopolist could squeeze?

In any case, monopolies aren't benign. They may successfully appear to be benign, but that usually has more to do with them successfulyl hiding their true costs than actually selflessly helping the consumer. Thinking otherwise belongs in the realms of ponies and ice-cream.
posted by acb at 10:52 AM on October 5

They may successfully appear to be benign, but that usually has more to do with them successfulyl hiding their true costs than actually selflessly helping the consumer. Thinking otherwise belongs in the realms of ponies and ice-cream.

Well, it depends on whether or not the monopolies are private companies or owned by the state. The NHS has a virtual monopoly on health care too, and next time I'm kicked by a pony while eating ice cream, I'll take it over the free capitalist's option, thanks.
posted by fightorflight at 11:53 AM on October 5 [1 favorite]

If it were practical to use ZIP codes for finding a segment of a street within short walking distance, Google would have presumably done so

Really?? I think you are confusing "Google is your friend" with "Google is God." (Mind you, I'm not disagreeing that ZIP+4 codes are not useful to the layperson for finding physical locations. But I find your assertion that "if it were useful, Google would have done it already" preposterous.)

Google Maps also doesn't display county boundaries (at least in the US), so I guess the division of states into counties is useless too.
Straw man. That's not what Google Maps does;

So when I present a feature that would be useful to have on a map (a feature I have specifically sought ought before, and was happy to find exists on Yahoo! Maps), your response is "that's not what Google Maps does?" I might as well argue that finding ZIP+4 codes is not "what Google Maps does."

It is not a straw man, and simply claiming that it is does not make it so. The observation that Google Maps does not display county boundaries—a feature, shared by many maps, which is useful in at least some situations—is a direct refutation to the argument that any feature which would be useful has already been implemented by Google Maps.
posted by DevilsAdvocate at 12:02 PM on October 5

Really?? I think you are confusing "Google is your friend" with "Google is God." (Mind you, I'm not disagreeing that ZIP+4 codes are not useful to the layperson for finding physical locations. But I find your assertion that "if it were useful, Google would have done it already" preposterous.)

OK, if Google hadn't done so, then Microsoft or Yahoo! or TeleAtlas or someone would have, and people would notice and start using their mapping service. If it were possible, Americans would be habitually punching ZIP+4s into the satnav units in their cars, in the way that Britons do postcodes.

I might as well argue that finding ZIP+4 codes is not "what Google Maps does."

This isn't about finding ZIP+4 codes; Google Maps doesn't find UK postcodes either. However, it can use them to find points. As can Yahoo Maps, Microsoft Live Earth, and in-car satellite navigation units. And, AFAIK, none of them can do this for ZIP+4.

Also, unlike (in most cases) finding a county boundary, finding a point from a postcode has some excellent use-cases. You can give someone a location, with sufficient precision to plan their journey, by texting them seven letters on a moblie phone. You can specify these points with less ambiguity and less risk of getting the wrong place. ("Did you mean: [ ] 125a Acacia Street, Hilldale, [ ]125 Acacia Avenue, Hilldale, or [ ]125 Acacia Street, Hillvale?") This is particularly useful when using journey planning services. In general, while the absence of such a street coordinate system isn't the end of the world, its presence does make things that much more convenient and does facilitate a lot of uses.
posted by acb at 12:59 PM on October 5

to further confirm a the might of royal mail when faced with a lack of postcode and house name:

[my friends name]
house with White gates near pylons
burton Leonard
England

...made it. i'm now trying to devise a cryptic address to see if postie can work out my parents address.
posted by 6am at 1:16 PM on October 5

Who managed to grab SAN TA0?

the buddha?

I used to experiment with seeing how little address, and how small a physical form, I could successfully send thru the mail. When I sent a 'postcard' that was the address written on the back of a stamp, they delivered it, but in a big envelope with a flier on proper mailing procedures, and a note that basically said "cut it out". Using zip+4 saved a lot of room.
posted by nomisxid at 3:11 PM on October 5 [1 favorite]

All extant geographic UK postcodes follow the pattern [A-Z]([A-Z]?)([1-9]?)[0-9]([A-Z]?) [0-9][A-Z][A-Z]. The UK post office issuing a code outside this framework should be considered as likely a possibility as that of the USPS issuing a place with a 6 digit zip code.

As I understand it, the pattern used to be [A-Z]([A-Z]?)([1-9]?)[0-9] [0-9][A-Z][A-Z], but then they ran out of codes in some areas, so they added that extra optional letter. My example of E12B 4RT actually matches your pattern, but apparently it's not (currently, at least) legal, since that extra letter can only be preceded by a single numeral. In any case, they appear to have changed the pattern before, so there's no reason to think it might not change again in the future to allow something like E12B 4RT or E132 4RT.

Just for amusement value, here's wikipedia's version of a regular expression that captures the current rules from the BS 7666 standard:

(GIR 0AA|[A-PR-UWYZ]([0-9]{1,2}|([A-HK-Y][0-9]|[A-HK-Y][0-9]([0-9]|[ABEHMNPRV-Y]))|[0-9][A-HJKS-UW]) [0-9][ABD-HJLNP-UW-Z]{2})

posted by klausness at 6:43 PM on October 5

No, the extra letter at the end has existed since the start, because central London had (large) numbered districts before postcodes were introduced, and they needed to subdivide them. Since they have this established method of extending districts that overflow, it's reasonable to think they aren't going to do something different in future. They haven't changed the basic format ever, AFAIK.

That regex is identical to mine except it accommodates the Giro number, disallows certain letters, and disallows an extra letter after a two digit number.
posted by cillit bang at 3:28 AM on October 6

But my point is that they could have easily made it a consistent, memorable pattern, such as xxn nxx. Using a combination of letters and numbers, rather than just numbers, is actually a good idea, since a six-digit alphanumeric code (especially one that usually contains at least somewhat meaningful letters) is easier to remember than an eight-digit numeric code (which is what would give you about the same number of codes). But then they had to screw it up from the outset by giving parts of London those special single-letter prefixes (with codes like E1 6QL) and making the first numeral actually a one- or two-digit number (with codes like NE21 4LY). And, of course, that optional extra letter at the end of the first block. Maybe it all makes perfect sense if you've grown up with it, but to those of us who haven't, it's all a bit arcane and needlessly confusing. And since postal codes are often used by people in other countries sending mail to the UK, I'd call that a significant design flaw. I think Canada got the alphanumeric postal codes right (presumably having learned from the flaws of the UK system).
posted by klausness at 4:23 AM on October 6

You're frocusing far too much on the letter/number positions. It's one of these followed by a number between 1 and 99, followed by a space and number, letter, letter, with the only potential variation being an overflow letter in the middle.
posted by cillit bang at 5:50 AM on October 6

From this morning's news: Legal threat closes postcode feed.
posted by immlass at 7:20 AM on October 6

The reason I'm focusing on the letter/number positions is because that's how most of the rest of the world (including all of the countries I lived in before moving to the UK) does it. Have a look at wikipedia's list of postal codes. Every other county on the list (aside from UK-related ones like the channel islands) has a single pattern for postal codes (OK, the US has two different patterns, but one is an extension of the other – kind of like the UK out code versus the whole postcode). The UK has six different patterns. For people in the rest of the world (who are used to looking at postal codes as a specific pattern of letters and numerals), that's kind of odd.
posted by klausness at 7:48 AM on October 6

"Kind of odd" describes a lot of the UK's practices.
posted by five fresh fish at 10:06 AM on October 6

There's now a petition asking the Prime Minister to encourage the Post Office to offer a free postcode database to non-profit and community websites.
posted by acb at 2:12 PM on October 6