After visiting the excellent Georgian Group today (special £15 membership discount for London Historians members), I took this picture of what struck me as being quite an old street sign. All to do with the “W” without a qualifying number. So how old is it? With the massive increase in postage during the early Victorian era, postal districts were introduced to London during 1857 and fully implemented by 1 January 1858. When further qualification was needed, the numbers with which we are familiar were added in 1917. So there we have it. Not exactly precise, but our sign dates from sometime between 1857 to 1917. The extra bits after the district code that we use for computerised sorting were implemented gradually during the 1960s up until 1974.
The furthest North London postal district is E4, Chingford; furthest East is SE2, Abbey Wood; furthest South is SE25, South Norwood; and furthest West is W7, Hanwell.
Much work on early post codes was done by the author Anthony Trollope, who worked for the Royal Mail. He was also instrumental in introducing post boxes.