London is a megacity of England/United Kingdom and even the world.
The current capital of the United Kingdom: formerly a county in its own right (1889-1965).
The geographical area covered is roughly the M25/the extent of the London Transport network.
The Wikipedia page for London is  and for England is . There is also a small England wiki at  and a smaller Britainpedia Wiki at .
If you have ancestors born or married in London, you may find their names at w:c:familypedia:London/bdm or w:c:familypedia:Greater London/bdm.