A postcode is a series of letters and numbers which are added to a postal address to make sorting mail easier. The US equivalent is a zip code.
The History of Postcodes in London
Before the postcode system, people would add a basic address to a letter and hope that it would arrive in the right place. The postal reforms in 1840 and the rapid growth of London’s population led to a greater volume of letters.
To try and have some organization, former English teacher Sir Rowland Hill was instructed by the General Post Office to devise a new system. On 1 January 1858, the system we use today was introduced and was rolled out to the whole of the UK in the 1970s.
To divide London, Hill looked at a circular area with the center being the post office at St Martin's Le Grand, near Postman's Park and St Paul's Cathedral. From here, the circle had a radius of 12 miles, and he divided London into ten separate postal districts: two central areas and eight compass points: EC, WC, N, NE, E, SE, S, SW, W, and NW. A local office was opened in each area for sorting the mail rather than taking everything to one central London location.
Sir Rowland Hill was later made Secretary to the Postmaster-General and continued to reform the Post Office until his retirement in 1864.
In 1866, Anthony Trollope (the novelist who also worked for the General Post Office) wrote a report that abolished the NE and S divisions. These have since been reused nationally for the north of England areas of Newcastle and Sheffield, respectively.
The NE London postcode areas merged into E, and the S district was split between SE and SW by 1868.
To continue to improve efficiency for the female mail sorters during the First World War, the districts were further subdivided into a number applied to each sub-district in 1917. This was achieved by adding a letter to the original postcode district (for example, SW1).
The districts that are subdivided are E1, N1, EC (EC1, EC2, EC3, EC4) SW1, W1, WC1 and WC2 (each with several subdivisions).
While the initial organization of the postal areas of London was divided by compass points, the further sub-districts were numbers alphabetically, so you may be surprised to find NW1 and NW2 are not neighboring districts.
The current alphanumeric code system was introduced in the late 1950s and finally completed across the UK in 1974.
London postcodes are more than just a way to address letters accurately. They are often the identity for an area and can even denote the social status of the residents in some cases.
Postal sub-districts are often used as shorthand to name an area, especially in the property market, as a W11 postcode is much more desirable than a W2 postcode (even though they are actually neighboring districts) leading to plenty of snobbery and inflated house prices.
SW = south-west London postcode area.
1 = the postcode district
A = as SW1 covers a large area the A adds further subdivision
1 = the sector
AA - the unit
The sector and the unit are sometimes called the incode and help the mail sorting office to divide the mail into individual post bags for the delivery team.
Not every property has a different postcode, but it will lead you to an average of 15 properties. For example, on my street, one side of the road has the same full postcode, and the even numbers on the other have a slightly different full postcode.
How to Use a Postcode
People used to be asked to add periods between each character (for example, S.W.1) and to write the town or city name in capitals (for example, LONDON). Neither of these practices is now needed.
When addressing mail to a London address, it is recommended to write the postcode on a line of its own or on the same line as 'London.' For example:
12 High Road
12 High Road
London SW1A 1AA
There is always a space between the postcode sub-district and the hyperlocal identifiers (sector and unit).
Royal Mail has a useful page to help you Find a Postcode to complete a UK address correctly.
The Newest London Postcode
As London is continually evolving with the addition of new buildings and new streets and the demolition of old structures and areas, the postcode system has to stay up to date. The biggest new postcode was added in 2011. E20 was once the fictional postcode for the TV soap opera EastEnders and became the postcode of the London 2012 Olympic Park in Stratford. (Walford, the fictional suburb of East London where EastEnders is set, was given the E20 postcode when the BBC launched the soap opera in 1985.)
E20 was needed, not only for the Olympic venues but for housing developments on the park in five new neighborhoods. Over 100 postcodes were allocated to developments being built across the Olympic Park to serve up to 8,000 planned homes in the Queen Elizabeth Olympic Park.
The previous highest postcode area in real-life East London was E18, around South Woodford. There is no E19.
The Olympic Stadium allocated its own postcode – E20 2ST.
Some Postal Districts
Here is a list of postcodes and the districts they relate to that you may come across on a trip to London. (Be aware, there are many more!):
WC2: Covent Garden, Holborn, and Strand
EC2: Bank, Barbican and Liverpool Street
EC3: Tower Hill and Aldgate
EC4: St. Paul's, Blackfriars and Fleet Street
W1: Mayfair, Marylebone, and Soho
W11: Notting Hill
SW1: St. James's, Westminster, Victoria, Pimlico and Belgravia
SW5: Earl's Court
SW7: Knightsbridge and South Kensington
SE1: Lambeth and Southwark
SE16: Bermondsey and Rotherhithe
E1: Whitechapel and Wapping
E2: Bethnal Green
N1: Islington and Hoxton
NW1: Camden Town