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I think he implied it but there are postal codes that refer to a single Mail Drop location.

For example, sometimes your tax return will have its own zip code in the USA.

At my university there were postcodes per large building
Any mail addressed to members of ships' crews on vessels transiting the Detroit River can be delivered to them via J. W. Westcott II by being addressed "Vessel Name, Marine Post Office, Detroit, Michigan, 48222." (wikipedia)
He should have written

  20
  SE1 6AD
  GB
and posted it in a different country.
Already on it! :)
I suppose it depends on the country you post from, but I'd expect "UK" to be more universally understood than "GB".
GB is the correct ISO country code for Great Britain.
I would not be confident in postal systems routing letters based on ISO country codes. If you send your letter in Tennessee with AR at the bottom of it, it's going to Arkansas or nowhere, not Argentina.
Yes, there are actually standard postal country names assigned jointly by the country concerned and UPU (the organisation that manages how mail works globally). For example, the correct country name for ISO GB is "UNITED KINGDOM" (https://www.upu.int/UPU/media/upu/PostalEntitiesFiles/addres...)

Pedantic: actually, there are (up to) two valid postal country names: the English one (UNITED KINGDOM) and the French one (ROYAUME-UNI, https://www.upu.int/UPU/media/upu/PostalEntitiesFiles/addres...). This is due to historical reasons: (jointly) Britain and the US (which use English) were the most advanced in postal services but the diplomatic language at the time is French.

GB is the correct ISO country code for Great Britain

But is the mail in the source country sorted by people, computers programmed by people, or by the ISO committee?

Funny, since Great Britain is not a country.
But eph is right. All addresses in "Norn Iron" have a UK postcode, beginning BT [for Belfast]. So while a letter addressed to...

Someone

BTXX XXX

GB

...would probably get there, it would technically be incorrect. Mind you...

Someone

BTXX XXX

UK

...might not get there either, if your postie was a dyed-in-the-wool republican!

That always trips a lot of people up because .uk is the country-code top-level domain for Great Britain, and cctlds are assigned using the 2-letter ISO country code for that country.

...except for Great Britain, who were one of the first few other countries to be connected to the internet, and decided to use .uk before people realised that every country would need one, and using already-assigned ISO codes would be the best way to hand them out.

Partially this is because the Joint Academic NETwork (JANET) in the uk used addresses in the form of xyz@uk.ac.qmc.cs according to wikipedia the JANET NRS had uk as the top level prior to dns adopting ISO codes in 1984 https://en.wikipedia.org/wiki/JANET_NRS
Huh? The country is called "United Kingdom of Great Britain and Northern Ireland", or the UK for short. Strictly speaking, if you talk about Great Britain, you're excluding Northern Ireland, but politically GB isn't a country...

Wikipedia says "Great Britain is an island in the North Atlantic Ocean", although historically there was also the Kingdom of Great Britain.

Well, go complain to ISO then, not me.

https://en.wikipedia.org/wiki/List_of_ISO_3166_country_codes...

Edit: Also, if you've ever seen UK teams compete in international sports, all their athletes have "GBR" on their team uniforms.

Yeah, GP is shooting the messenger. If the GP is reading this, here is the address of the ISO 3166 Maintenance Agency:

  ISO 3166-1:2020: Codes for the representation of names of countries and their subdivisions — Part 1: Country code
  ISO 3166-2:2020: Codes for the representation of names of countries and their subdivisions — Part 2: Country subdivision code
  ISO 3166-3:2020: Codes for the representation of names of countries and their subdivisions — Part 3: Code for formerly used names of countries
  
  Maintenance Agency
  
  ISO 3166 Maintenance Agency
  c/o ISO Central Secretariat
  BIBC II
  Chemin de Blandonnet 8
  1214 Vernier
  Switzerland
  
  Tel: +41 22 749 01 11
  E-mail: customerservice@iso.org
  Website: www.iso.org/mara/iso3166
Letters like K for kingdom are generally avoided in codes, since this way a change of constitution to the Republic of Great Britain and Northern Ireland doesn't require a new code.
UK is also more correct because it includes Northern Ireland and the other smaller islands (which are not in Great Britain, the main island)
It's only more correct if the address is in Northern Ireland or one of the other islands that make up the UK but not Great Britain - which London is definitely not.
Although interestingly, Northern Ireland and the Channel Islands have the ISO country code GB, but Gibraltar (GI), the Isle of Man (IM), the Falklands (FK), and many others do not. Some are Crown Dependencies, which I suppose is understandable, but others are part of the UK.
Gibraltar and the Falkland Islands (among a few other places) aren't crown dependencies or part of the UK, they're the vestigial remnants of the British Empire that rejected full independence for various reasons. Until around the time of the Falklands War they were still called crown colonies but they're now called British Overseas Territories. They're not like France's equivalent where many are integral parts of France.
Even then, the Channel Island are a Crown Dependency and use the GB ISO code, while the Isle of Man is also a Crown Dependency and has its own ISO code.

The British Indian Ocean Territory and the British Antarctic Territory are both British Overseas Territories, but unlike the Falklands, Bermuda, etc, do not have their own ISO codes.

So the determination is more complex than that.

These have codes GG, JE, IO.

Claims of Antarctic territory aren't recognised internationally, so the codes were removed, but it used to have the code BQ.

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In fact, in some European countries it was until recently general usage to prefix a postcode with the country abbreviation for cars,[0] i.e., A for Austria, B for Belgium, D for Germany, FIN for Finland, H for Hungary, NL for the Netherlands, SLO for Slovenia, etc. But I guess the ISO country codes are now at least as well recognized and will also work.

[0] http://www.columbia.edu/~fdc/postal/#europe "After World War II and up until the mid-1990s, all European postcodes included country-code prefixes. These were originally United Nations "car codes" (one, two, or three letters), kept in an annex, "Car (Or Road) Distinguishing Signs", to the 1949/68 United Nations Conventions on Road Traffic, adopted in part by the European Conference of Postal and Telecommunications Administrations (CEPT). These codes were not accepted by the Universal Postal Union as a world standard, but were widely used anyway."

It would be one char more minimal if he moves from "SE1" to e.g. the "N1" area.
You can put just ‘HMRC’ (UK tax department) on a letter (with paid postage) and it will get to them.
...and, if you write to a member of parliament at the Houses of Parliament, you don't have to use a stamp.

So presumably...

<MP name>

HP

...with no stamp on the envelope could theoretically work.

Now, which MP has the shortest name?

No stamp required is due to “Franking privileges”. Same as in Canada.
US Congress people also have “franking privileges” but it only applies to outbound, not inbound mail.
Ed Davey, Tom Hunt, Rupa Huq, Ben Lake, Ian Levy, Alan Mak, Lia Nici, Naz Shah.

I daresay "A Mak" or "R Huq" would work too.

Since not including a stamp should imply it's for an MP maybe it would be enough to choose a unique short name. I think there's more than one Ed, but Lia or Naz should be sufficient.
Actually, thinking about it "PM" should be sufficent to address it to the Prime Minister. So...

PM

HP

Might work. Maybe I should go and parcel up some dogshit and try it.

Can we go shorter? The Director General of MI6 traditionally has the designator 'C'. This probably wouldn't work anywhere in the UK, but if you dropped it off at a Post Office near Vauxhall Cross, they'd probably figure out what you meant.
I believe DVLC would work too (now DVLA, iirc).
There are also freepost addresses, where you can write "Freepost CompanyName" with no postage. I've found one on google which is just "Freepost OAL".
In Ireland it's just XXX XXXX (each property gets assigned with a unique EirCode)
And in Dublin, the first three exactly match the city area (e.g. D01 for Dublin 1) -- though outside the city the first three become less obvious.

Just the same, it's incredibly annoying that ecommerce sites still generally require full addresses rather than just using the An Post Eircode lookup thing to map an entered Eircode to an address.

Although An Post don't use EirCodes, so I wonder if an EirCode alone is enough?

Source: https://www.thetimes.co.uk/article/an-post-staff-fail-to-use...

Interesting large delivery companies do not use EirCode either. It was not primarily designed for deliveries but taxation. It's still annoys me to this day.

The Irish government had a problem administering Property tax and the TV Licence due to data sharing restrictions between departments. Unique Eircodes per property was the solution. This was explicitly stated by the Communications Minister Pat Rabbitte at the time of launch. The proposed Broadcasting Charge to replace TV licenses was not rolled out due to public opposition but EirCodes remain. Due to their random nature they are also less useful to emergency services.

Delivery companies have taken courtcases against the government over the EirCode rollout and there is an ongoing courtcase over allegations of corruption relating to the awarding of the EirCode contract[1].

[1] https://www.irishtimes.com/business/2022/11/28/firm-claims-c...

> Due to their random nature they are also less useful to emergency services.

That's not my experience at all. They've been a revolution in address resolution at NEOC in my experience, and they're used for navigation on nearly every emergency call.

If I write just an EirCode on an envelope the letter would be delivered anyways.
Are you sure? It might be a case of someone in the system Googling the address and writing it in.
I've tried to do that several times, it always worked. I don't know why/how but it works.
Clearing out some old stuff from my grandparents, grandpa had at some point received a letter, from Stockholm, to their summer house in the woods addressed

    Thorvald
    The forest by <tiny village in Sweden>
I've seen things done like that here in the US also. Something like...

  First Name, Last Name
  Blue house down by the creek, next to a yellow shed
  State, Town, Zip
It works, sometimes. I think it's up to the postal carrier if they want to really try or not.
That's why it pays to be extra nice to your postal carrier. I've gotten a couple of packages delivered where the international sender clearly had no idea what a US postal address looked like, my name was completely mangled, but the zip code got it to the local post office and my carrier apparently said "there's only one person on the route who gets packages like that".
I remember from one of my first jobs, we received a vacation postcard addressed to:

- Dear friends - Lange voorhuid - Holland

.... Lange voorhuid was a mis-spelling of the streetname: "Lange Voorhout", which is someone unique to The Hague... but didn't have a housenumber (and it's a long street). Still, the postcard arrived at our company before the sender got back from vacation.

The dutch postal service is honestly kinda impressive with this sort of thing. I'm pretty sure they keep a name-address database or some such, because mis-addressing a letter will still almost always get delivered correctly based on the name.

IIRC it's fairly recently they stopped delivering to non-postal addresses. i.e. until recently you could address something to "The green house next to the church" and it'd get there.

My parents, living in rural Norway, received a postcard simply addressed to their first names, Norway.

It turned out they were the only couple with that exact combination of first names, and someone at the Norwegian Post were bored enough to ask the Folkeregisteret (the database in which all Norwegians are listed) whether there were any Jorunns living with any Ingolfs anywhere in the country.

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I once received a post card from my little sister as she was backpacking in Australia.

It only had my name and "Finland" as the address.

The card came with a special sticker "This item passed through the post office special mail resolution."

Sounds like someone had a boring day in a work in the post.

In the Netherlands you can do something similar. Postal code + house number is unique for a box (there can be no multiple boxes at a single house number), and all other info is optional.

So, a full address could be: 1540 AB 1.

Definitely not unique to Japan, but several towers here have their own zip code, and there is at least one building I know where the building has several zip codes (each for various floors of the building).

People take this and extrapolate to think that we should just be writing very long zip codes for everything, but the wonderful nature of writing out addresses is that they have a lot of possible error correcting. The one thing that is still pretty haphazard is the street number, let's get some ECC checks in there!

A building in the UK with about 300 apartments will prob have around 8 postal codes
I've been in at least two apartments blocks that had multiple post codes, but that's not hugely unusual as a UK post code is (to a first approximation[0]) a street identifier, so the high street has one, the side street has another, and the rear parking might also be its own.

In one case, this meant my front door and back door had different post codes, even though it was a 35 square metre one bed apartment.

[0] except when it isn't https://en.wikipedia.org/wiki/Postcodes_in_the_United_Kingdo...

Well it's all going to a central place in the flats, so without a specification on which flat how do we know which flat the letter belongs to - works well with a house you own but the minimalism could mean your post being inadvertently taken.

However it's a good show of how much ink/time is wasted normally on letters with useless data.

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At risk of sounding like a sourpuss, I can't help but think that this is something that most people who live in the UK work out simply by using web forms which autocomplete your address based on simply postcode and number.
And that reasoning of writing the form to just be postcode and flat number is why I can't get my address into forms.

There are two flat 1s in my postcode.

One place that would not work was the local council and so I could not get anything done, it took over a year of phoning up for this to be fixed. (of course the council tax database got it correct)

I wish companies would fix their addressing. My address has the form:

1 Example Close Somewhere Drive

But often when entering your postcode and selecting a house number, the address ends up as "1 Somewhere Drive" - which is a different place. The forms don't seem to realise that some locations should have multiple address lines. Fortunately in the UK, the postcode helps ensure our mail (mostly) arrives.

I've always assumed it but this guy actually tested it out, and so he gets credit for that
I remember working with SagePay as a payment provider back in 2008 (before we knew of Stripe!) and finding it interesting that card address validation was only done on the numbers in a full address.

For example, from "20 Windsor Road, London, SE1 6JH" it would extract 2016 and validate that against the banks details.

I thought that was quite a smart way as UK addresses can come in all forms, shapes and sizes (as the post shows) – but the minimal bits required to be correct are indeed the numbers as all postcodes have them and an incorrect number would mean a incorrect postcode.

Edit: the funny bit was that they made you work this out and send it along with the request rather than just handling it internally :)

How would it work where the house has a name instead of a number e.g. Wisteria cottage, Bristol, BS1 1AA?
I presume that ‘hashes’ to 11.
Correct. Which means if you’re taking deliveries it’s probably better to have a house number as you get validated more frequently.
I live on a road where all the houses on one side were built first and numbered 1 2 3 4... The houses on the other side were built later and have names and no numbers.
In the US, PO Boxes often have their own ZIP code. I used to be able to be reached from anywhere in the world by:

01004-0072 US

Interesting, I tried something similar here in the US by using an address like this:

1 my street

01234-5678

But the letter was returned to me as "Address Unknown". It needed the City and State to be delivered. Nice to see in the UK the postal codes are more useful then here in the US.

Think of it as a checksum, not an IP address.
This can be hit or miss, I remember when younger I got a letter to our PO Box with just the ZIP+4 (the ZIP is unique for a post office, and if there are less than 10000 PO Boxes, the +4 is unique for the box).

Part of it can come down to if the postman wants to bother to figure it out.

I am looking at this and thinking of the systems we build (in software) and what we can learn from the sublime postal system.
Reminds me of this wonderful post, primarily UK oriented. Falsehoods programmers believe about addresses https://www.mjt.me.uk/posts/falsehoods-programmers-believe-a...
I'll add one: An address with an apartment letter may not be the same building as the same address without the apartment letter. My address is something like "Bijvorbeeldstraat 3B". Next door, in a separate building, is "Bijvoorbeeld 3". Most services (including the national population register!) insist that I enter my address as "Bijvoorbeeldstraat 3 bus B", which results in (for everybody except the national post) coming to "Bijvoorbeeldstraat 3" and my deliveries getting marked as "nobody home".

In particular, I'm looking at you Uber Eats/Deliveroo. I get whinged at by roughly half the delivery drivers who come to deliver my food for putting in the wrong address, despite having delivery instructions that include a description of the correct door.

Years ago I was told that in Canada house number + postal code was sufficiently unique to deliver mail. This made sense to me in a design, it drastically cuts the amount of information that needs to be read off the envelope.

Then I bought a house that shares a postal code and number with a house on the street behind.

It’s had me wondering what the minimum viable address for any address in the country would be.

I wonder if there are performance differences/overheads between the address styles?

Maybe automated sorting machines use redundant information for OCR error-correction, and omitting it might kick the letter into a fallback "manual processing" queue as the automation has no way of checking the validity of its guess?

In terms of buildings/mail unit, an example of a post code in the UK would be CB2 1TQ which is for Trinity College.
I know that many constituent colleges at the University of Cambridge are the only address in their post code. For example, Trinity College is CB2 1TQ.

However, hundreds of people live in each college (they just have large mailrooms), so on a practical level you’d likely need to put your name down if you wanted to get mail.

Postcodes in Poland are much less granular than the UK ones, but you can still get by in more rural areas on the assumption of local postmen knowing the people. My parents used to routinely successfully receive letters addressed just

<my parents’ names> <town name>

where the town has circa 3K inhabitants.

Many people don't realize that in the USA, the letters only get sorted by postal zip code (and sometimes zip+4) - everything else is sorted by the postman as he walks the streets, so if your letter gets to the right post office it will likely get to the right postman and he can often figure it out without it even having to go to the dead letter office.
It looks like it went through the automated letter sorter, too (see the orange barcode that's been added to the envelope). Not surprising as the address is even more unambiguous to a machine than a human.

Occasionally there are viral stories here of letters being addressed to places like "The blue house, Termonfeckin, Ireland", which looks like it conveys less information even if it's physically longer. These get manually sorted, though.

> It looks like it went through the automated letter sorter, too

I understand the mail sorting depots can x-ray scan and read the contents of letters up to 4 pages of a4 folded, but that could have been hackers feeding me fake info in order to stop me writing letters.

An example of the technique https://www.theguardian.com/books/2021/mar/02/researchers-re...

I'm not aware of any postal service that uses a method other then optical imaging for address reading. Further, in some countries such as the US, it is not legal for the postal service to "look inside" mail pieces without a warrant.

While this type of 3D X-Ray technique is indeed possible it requires expensive specialized equipment and a great deal of effort, thus it being a major achievement for this university group. Or in other words, if a research group puts out a press release lauding a first, it is not likely to be a technology in use in thousands of sorting centers for millions of mail pieces daily.

> I'm not aware of any postal service that uses a method other then optical imaging for address reading. Further, in some countries such as the US, it is not legal for the postal service to "look inside" mail pieces without a warrant.

It could be hackers exploiting my lack of knowledge to social engineer me for their own criminal gain then. They even mentioned some of the old postal machines were for sale on ebay.co.uk, so when I looked there were 2nd hand postal xray machines for sale.

There's a difference between spotting a bomb in a parcel and reading the instruction manual.
The conversations I saw claimed they could read the ink on upto 4 sheets of A4 folded in an envelope. It may have been a form of social engineering, because I'm aware state hackers ignore laws and invade peoples privacy and enter their homes through the resident's internet connections.
X-ray is not that unusual to check for contraband at customs, although it depends on the country whether or not it is a routine practice or requires suspicion. Perhaps the UK does so on domestic mail as well but that would be surprising to me, it's pretty high cost to do at large volume. These X-ray machines are the same type used at airports and usually produce either a synthetic isometric 3D-type image or two 2D images at 90 degree offset. The resolution and sensitivity are both nowhere near high enough to read text on documents, they're primarily oriented at recognizing firearms and very dense objects typical of drug smuggling. Much of the data modern X-ray parcel scanners produce is synthetic as well, based on machine vision and multi-exposure methods, so the display tends to suggest that the data they collect is of higher resolution than it actually is.

You would struggle to determine whether a page is folded A4 or A8 with one of these machines, reading text is far beyond their capabilities.

The Royal Mail in the UK is definitely allowed to open mail as a last resort to figure out where it should be returned to, the National Returns Centre undertakes this work. If the contents turn out to be something that isn't returned (e.g. a newspaper or magazine) it's destroyed, if it's a letter the NRC will try to figure out where it came from and send it back there.

Most commercial mail carries an return address written on the reverse to avoid the need for this, and of course letters you write by hand should also provide a return address in principle although you're much less likely to send stuff to the wrong address than a commercial operation - when I heard my cousin had moved just before Xmas I didn't send her a card, because there's no point sending it to the wrong place and hoping it gets forwarded eventually, it's just an Xmas card.

That orange barcode could've been added by a human too. The entire sorting process only relies on that barcode, so once a human decodes the address and adds that barcode it'll just work.
If you expect the post office to manually guess the normalized address from the incomplete form, just a unique narrow area name and your name alone should suffice.

That is, if you have a name unique enough in that area.

I once got USPS mail addressed to:

My name My town (slightly misspelled), My State

no zip code, no mail box number. The beauty of being in a small town where the postmaster knows who you are.