London postal district

From the longer Wikipedia page

The London postal district is the area in England of 241 square miles (620 km2) to which mail addressed to the LONDON post town is delivered. The General Post Office at the control of the Postmaster General directed Sir Rowland Hill to devise the area in 1856 and throughout its history has been subject to gradual periodic reorganisation and division into increasingly smaller postal units, with the early loss of two compass points and a minor retraction in 1866. It was integrated by the Post Office into the national postcode system of the United Kingdom during the early 1970s and corresponds to the N, NW, SW, SE, W, WC, E and EC postcode areas. The postal district has also been known as the London postal area. The County of London was much smaller at 117 square miles (300 km2), but Greater London is much larger at 607 square miles (1,570 km2).