The Amazing World of Postcodes

How Postcodes Improved Life in Britain…

Postcodes are so commonplace now that we never consider how important they actually are. The fastest and most reliable way of getting to a destination or sending mail in the UK is by including a postcode. Without a postcode, things would be a lot harder.

The humble UK postcode that we know today has been around since 1959. Although the main UK-wide system launched in 1959, a hundred years earlier London had already introduced a system of postal subdivisions.

Originally conceived to help the postal service locate addresses to deliver letters, UK postcodes are now a critical classification system for a whole range of planning, mapping, evaluation and analytical systems, from in-car sat-navs and courier routing to insurance risk assessment.

The Royal Mail’s Address Management Unit maintains the official UK postal address and postcode database on its Postcode Address File. This is available under license for a fee and is regulated by OFCOM. Most addresses can be constructed from the postcode and house number – when you register or order online, this is the data that enables you to select your address using the website owner’s address management software.

Postcodes are a great basis for geodata, but they’re not infallible. Some postcodes cover so many buildings that it can be difficult to isolate the correct address. Others sit on top of each other in large blocks of flats or belong to a Royal Mail sorting office for onward delivery. They don’t give any information about the nature of the building (house, flat or commercial premises) or access to it. Depending on what you need postcode data for, you may need an enhanced or supplemented dataset that provides more accurate co-ordinates or combines with demographic, geographic or commercial data to give you a reliable basis for decision-making and planning.


Postcode Facts:

  • There are around 1.8 million live UK postcodes, but did you know that every year new postcodes are created, changed, moved or taken out of use? In the last year there have been over 15,000 new postcodes created, and over 28,000 postcodes moved their location more than 40 metres to make them more accurate (CACI keep a record of over 700,000 historic postcodes).
  • You can’t buy a personalised postcode in the same way that you can buy a personalised number plate for your car, but the Royal Mail sometimes allocates mnemonic codes to high profile organisations. For example, DE99 3GG for Egg Banking, E16 1XL for London’s Excel Arena, SW11 1US for the American Embassy in London and S14 7UP for The Crucible in Sheffield, a nod to the maximum break in snooker (147 up), which it famously hosts.
  • The biggest unit postcode in the United Kingdom is IV27 4NZ, covering 442 square kilometres in Lairg, Scotland – that’s only slightly smaller than the entire country of Andorra (468 square kilometres)
  • There are nearly 1.5 million postcodes in England. Scotland has just 158,000 and Wales fewer than 100,000, while Northern Ireland has just 49,069
  • The most densely populated UK postcode is the W1T 5 sector, with 49 people per km2 in the Fitzrovia area of London
  • The term “postcode lottery” has become a metaphor for unequal access to services. There is also an actual “postcode lottery” – a subscription lottery that raises money for charities, earning winners cash prizes if they sign up with their postcode and pay £10 a month.
  • 10 Downing Street has the postcode SW1A 2AA






Using postcode data but it’s not good enough? Wondering how to augment your postcode data to get more accurate business results? We can evaluate the many geodatasets available to recommend the most suitable combination for your needs. Get in touch with us here.