This project defines its coverage as the area within the M25 orbital motorway but extending beyond this as follows:
- Where the London Underground stretches beyond the M25. Hence we cover Amersham, Chesham, Chalfont and Epping too.
- Where the administrative Greater London stretches beyond the M25 – the single case of North Ockendon
- Areas of the former county of Middlesex beyond the M25: Potters Bar, South Mimms and Poyle
What defines ‘London’ is open to interpretation. Since 1965, there has been an area officially referred to as Greater London but London’s postal area – the area covered postcodes beginning E, N, NW, W, SE, SW, WC and EC is another definition – though part of E4 lies outside the administrative area known as Greater London.
The small ancient City of London at its core once comprised the whole settlement, but as its urban area grew, the Corporation of London resisted attempts to amalgamate the city with its suburbs , causing “London” to be defined in a number of ways for different purposes.
Forty per cent of Greater London is covered by the London post town, within which ‘LONDON’ forms part of postal addresses. The London telephone area code (020) covers a larger area, similar in size to Greater London, although some outer districts are excluded and some places just outside are included. The Greater London boundary has been aligned to the M25 motorway in places.
Outward urban expansion is now prevented by the Metropolitan Green Belt, although the built-up area extends beyond the boundary in places, resulting in a separately defined Greater London Urban Area. Beyond this is the vast London commuter belt. Greater London is split for some purposes into Inner London and Outer London.
The city is split by the River Thames into North and South, with an informal central London area in its interior. The coordinates of the nominal centre of London, traditionally considered to be the original Eleanor Cross at Charing Cross near the junction of Trafalgar Square and Whitehall. However the geographical centre of London, on one definition, is in the London Borough of Lambeth, just 0.1 miles to the northeast of Lambeth North tube station.