London is the capital of England and the UK. It is the UK's largest and most populous metropolitan area and the largest urban zone in the European Union by most measures. London has a diverse range of peoples, cultures, and religions, and more than 300 languages are spoken within its boundaries. In July 2007 it had an official population of 7,556,900 within the boundaries of Greater London, making it the most populous municipality in the European Union.

The Greater London Urban Area (the second largest in the EU) has a population of 8,278,251  while the metropolitan area (the largest in the EU) has an estimated total population of between 12 million and 14 million. The London Underground network, administered by Transport for London, is the most extensive underground railway network in the world, London Heathrow Airport is the world's busiest airport by number of international passengers and the airspace is the busiest of any urban centre in the world.

Source: Wikipedia