Greater London is often referred to as "the City" or "the Square Mile" and it forms the main financial district. Archaically, the urbanised area of London was known as the Metropolis. In common usage, the terms "London" and "Greater London" are usually used interchangeably. Greater London is officially divided for some purposes, with varying definitions, into Inner London and Outer London. For some strategic planning purposes it is divided into five sub-regions. Greater London is under the strategic local governance of the Greater London Authority (GLA). It consists of an elected assembly, the London Assembly, and an executive head, the Mayor of
Central London media". For strategic planning, since 2011 there has been a Central London sub-region comprising the boroughs of Camden, Islington, Kensington and Chelsea, Lambeth, Southwark, Westminster and the City of London. From 2004 to 2008, the London Plan included a sub-region called Central London comprising Camden, Islington, Kensington and Chelsea, Lambeth, Southwark, Wandsworth and Westminster. It had a 2001 population of 1,525,000. The sub-region was replaced in 2008 with a new structure which amalgamated inner and outer boroughs together. This was altered in 2011 when a new Central London sub-region was created, now including the City of London and excluding Wandsworth.