Victoria Summerley: Town Life

After all the recent furore about postcodes and fashionable locations (who wants to live in Notting Hill anyway?), it's tempting to suppose that it's all the result of some great plot foisted upon us by the Royal Mail to keep us in our place and stop us tacking a couple of hundred grand more on the price of our properties.

I can just imagine a dusty committee room somewhere within the bowels of Mount Pleasant sorting office, where a group of Royal Mail employees, copies of Socialist Worker sticking out of their back pockets, are poring over a map of Greater London, withering the social aspirations of its inhabitants with the help of a compass and a ruler. "Let's really wind up those yuppies in Battersea and call SW8 North Mitcham," they chuckle over their mugs of builders' tea.

Socialist principles, I'm sorry to say, have nothing to do with it. On the contrary, one could argue that there is some evidence of forelock-tugging in the allocation of some postcodes. Buckingham Palace, for example, is SW1A 1AA while 10 Downing Street is merely SW1A 2AA. (The House of Commons, though, is SW1 0AA - perhaps because it's full of zeros.) Nor is it down to old municipal boundaries, the London Assembly, or historic electoral constituencies. The postcodes are there simply to make it easier to deliver the post.

Yes, world wars have come and gone, constituency boundaries have been drawn and redrawn, slums have been gentrified, new Tube lines built, the East End bombed to bits, Docklands regenerated and the government of London itself abolished and re-established. And in the middle of it all, the Royal Mail has simply got on with the job of delivering the post across the capital in its own idiosyncratic way. Until 2003, it even had its own underground railway that connected the main sorting stations from east to west.

London is unique in the UK in having postcodes based on its geography rather than on the name of the metropolis (unlike Windsor and Maidenhead, where the SL postcode, which refers to unglamorous Slough, has caused so much angst to residents of the Hyacinth Bucket variety.)

The old postal districts of London - SW, NW and so on, which you still occasionally see on old Victorian street signs - were introduced in 1858, nearly 20 years after the introduction of the penny post democratised letter writing. The numbered subdivisions - SW11, SW18 etc. - were introduced in 1917, when wartime correspondence had pushed the volume of mail to unprecedented levels. It is these divisions that have become part of the language that London still uses, 90 years later, to describe its neighbourhoods - "I live in SW18, you live in SE11, he and she live in W1 (the rich gits)."

Some postal districts go further than others: SE goes all the way up to 28 - the new town of Thamesmead, which used to be part of SE2, necessitated using an additional code - while there are only 11 NW divisions. SE2, or Abbey Wood in the London Borough of Greenwich, is the easternmost postcode and E4 extends the furthest north (Chingford and Highams Park). The western boundary is W7, or leafy Ealing, and the southernmost tip is SE25, in the balmy environs of Woodside and South Norwood. Strangely, there are no London postal districts called S or NE.

The next bit of the postcode, the letters bit, was introduced between 1960 and 1974, following a trial in Croydon, which was chosen because its third letter could also be a digit. The CR0 district still contains more postcodes than any other district in the UK, though ironically the zero in CR0 initially caused the Royal Mail software to play up. (Isn't it wonderful to be British?)

Nowadays, although every mail order company can summon up your address from your postcode, the Royal Mail finds that the system doesn't work well enough and has introduced a new coding called Mailsort.

Which may or may not explain why, wherever you live in London, whatever your postcode might say, and however smart your neighbourhood may be, the postman still insists on putting letters addressed to someone in the next street through your letterbox.