What counts as central London and what doesn't is one of those debates that can run right through until closing time in the pub. The fact is, no one method is completely accurate and with such a large amount of people in such a small space, drawing a line anywhere is difficult.

London's borders are constantly changing and always moving outwards, what began as the Roman city of Londinium soon merged with the neighbouring city of Westminster to form the giant conurbation that swallowed up nearby towns such as Southwark and Hammersmith. Central London was governed by the London County Council (LCC) from 1889 to 1965. In 1965 the Greater London Council (GLC) replaced the LCC and covered a wider area, in addition to Central London large portions of adjacent counties were included. Big chunks of Middlesex, Essex, Kent and Surrey were now considered part of a Greater London metropolitan area.

In 1986 the GLC was controversially dissolved by Margaret Thatcher, the GLC had a strong Labour leadership and this was a constant headache to Thatcher's Conservative government. For almost 15 years power was devolved to borough level, resulting in wildly different policies in different areas of London. Towards the end of the 20th century, the ruling Labour powers were keen to restore a leading council for London. In the year 2000, Ken Livingstone was elected as the first mayor of the new Greater London Authority, this broadly includes central London and all of the surrounding borough councils within the M25 motorway.

Central London is usually said to be anywhere defined by the Royal Mail as being in the postal area of London, these are easily identifiable as places with a postcode beginning with W, SW, SE, E, N or NW. Anywhere outside these postal areas but still within a London Borough is Outer London. Postcodes are a handy way of defining London since they are rarely changed, unlike the political boundaries.

The densely populated parts of central London are further divided into WC and EC postal areas. WC mostly corresponds to the West End, places such as Soho, Leicester Square and Covent Garden, while EC is home to the square mile of the financial district and the historic city of London.

Outer London postal areas are UB and HA for Uxbridge and Harrow to the west, EN, IG and RM for Enfield, Ilford and Romford to the north and east, DA and BR for Dartford and Bromley to the south-east and CR, SM, KT and TW which lie to the south-west and represent Croydon, Sutton, Kingston-upon-Thames and Twickenham.