Something that permeates most of our lives but which we give hardly a thought to is the Post Code, that short set of digits at the end of an address that more than anything above it ensures letters get to the correct place.

And an exhibition about the history of the Post Code has opened, appropriately enough at the Postal Museum.

Starting with one of the museum’s most asked questions, an introduction to how postcodes work, the exhibition jumps back to the beginnings of postcodes in London, the introduction of machines to sort letters by postcodes, their spread outside London, and how people reacted to them.

Pride of place is ELSIE, the UK’s first ever mechanical letter sorting machine. Although it actually had a human operator who typed the sorting code in for each letter, and the machine shuffled the letter to the correct pile for delivery.

During the first demonstration to the government Minister and media, it was noted that the ELSIE machine was impressively quiet in action, which was attributed to British engineering skills. In fact, the conveyor belt had broken before the demo, so they never switched it on and hid a couple of staff to drop letters into the sorting slots when people pressed buttons on the front. The post office’s Mechanical Turk passed the demo undetected, and finally, the idea of machine sorting of letters was possible.

You can also play with a simulation of ELSIE in the museum, with the static machine sitting in front of a digital display that simulates the dexterity needed by post office staff to read addresses and enter the correct postcode. Your correspondent failed, badly.

Although they had expanded outside London to the main cities, the postcode was still a piecemeal idea, and it wasn’t until as recently as the 1970s that it was decided that the whole UK would adopt the postcode for every address. Being still a new idea for many people, something I’ve never seen, which may show my London centric outlook, was Poco the Elephant, a marketing scheme cooked up in the 1980s to promote PostCodes to younger people.

There’s a lot of ephemera on display, from the internal letters sent when planning the national rollout of the postcodes, to documents from the post office’s secure research labs in Dollis Hill (and home to the Paddock war bunker), and feedback postcards which were often less used to give feedback about the postcodes, than the cost of a postage stamp.

There’s a lot to see, and some things to play with.

The old 1970s adverts are nostalgic, the monopoly-esque postcode board game is weird. The blue dot trials of putting glow-in-the-dark dots on letters as they were scanned by post office machines is something I had never seen before. I squealed in delight when I saw the exhibition included a Poco the Elephant branded Sinclair flatscreen TV, given away as prizes. Just as successful as the TV in sales, was the Postcode song, with music by Postman Pat composer Bryan Daly.

Postcodes are an oddity in some regards. Introduced to London 150 years ago, and yet also launched within living memory for many people outside London. Something that was designed to improve the sorting of mail and cut costs is now also something that people often use to define where they live.

People living on the edges of London can be quite passionate about whether their postcode means they live outside London, in say a Kingston postcode, or in Greater London, which is what their council represents. This is a bit odd as postcodes are a sorting system for postage based on where the post office sorting offices are. They are not geographic in the human sense, and yet we’ve adopted them as shorthand code for where we live.

Write a London address with SW on it, and instantly an image forms in your mind about the sort of place that letter is going to and the person it’s addressed to. In that, the British postcode is more interesting than say the USA’s zip code, which is numeric. The British one based, loosely on the first letters of the town still feels connected to the region, even if the computer scanning the addresses today would probably prefer numbers.

As the exhibition also shows, postcodes are used to categorise not just addresses, but people. The people who tend to live in similar areas tend to be similarly rich or poor, and that information is very useful to anyone from salespeople to charities to politicians.

So the postcode, designed to sort postage, is used to sort people.

There’s a big table-top screen where you can type your (or someone you know) postcode in and it will give you your area’s demographic profile. It seems I am older than my neighbours.

The postcode has become so essential to daily life that residents of new buildings can find that their homes “do not exist” for several years after they move in. That’s because the Royal Mail which maintains the postcode database, the PAF, charge for it, and companies can decide how often they will update their own local copies.

Many companies opt for the cheaper annual update, or when they can be bothered to update their systems.

So brand new postcodes created when needed can, very annoyingly, take a few years for some sluggish organisations to find out about. In fact, the Postal Museum is large enough to have been given its own postcode (WC1X 0DA), and for a few years after it opened, the museum of postage had problems with other companies unable to recognise its address.

As an exhibition, assuming you find the museum with your postcode locator, is a good walk through the history of something most of us use without a second thought.

The exhibition, Sorting Britain: The Power of Postcodes, is at the Postal Museum in Farringdon until the end of this year

Entry to the exhibition and a ride on the Mail Rail is £16 for adults, and tickets can be booked from here.

Exhibition Rating


The Postal Museum
15-20 Phoenix Place, London


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  1. Geoff m says:

    There was a demonstration of postcodes at the Science Museum in about 1968. After all the fascinating automatic sorting machines and special stamps you could send a postcard with minimal address but full postcode. You posted it in a special post box and Royal Mail delivered it free. It usually arrived the next day (mine did).

  2. Chris rogers says:

    That’s neat. When I toured Mount Pleasant the operator told me where I lived just from my postcode. My piece in the 60s WCDO mechanised sorting office may be of interest

  3. Peter Johnson says:

    When the national rollout was started it was called the Postal Code. The same alpha-numeric system was adopted in Canada. So far as I know they are the only postal systems that sort to streets or part of streets. US zip codes, for example, route to areas.

  4. Betterbee says:

    AIUI US Zip+4 codes sort to delivery rounds, similar to UK postcodes.

  5. Chris Page says:

    The article says, ‘the exhibition jumps back to the beginnings of postcodes in London’. I wonder why it doesn’t jump back to the beginnings of postcodes in the UK. The first place to use postcodes was Norwich.

    Initially, the code for my parents’ house in the early ’70s was NOR 84Z but in due course it was changed to NR13 4JY.

    It’s weird how I still remember those, but it must be one of those memories ingrained in one’s brain forever. I still remember our first phone number from the late ’60s – Markyate 566 (party line!) and the registration of my mother’s 1963 Mini Cooper – 529 FXU. Can’t remember what I was doing a week ago though!

    • ianVisits says:

      Norwich was not the first place to use post codes, as is explained in the article.

  6. Emma B says:

    I will DEFINITELY be going to this. Good to know the Postal Museum shared a problem I had in the mid 90s. I lived in a converted phone exchange – single building in the postcode – and it was the early days of online shopping. Regular fails on the validity of my postcode meant I would have to use the workplace one round the corner. Coincidentally, my job there required mailing list updates, often looking up postcodes in the massive PAF folder…

    I do hope they’re selling this to visitors.

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