Riots At G20 Summit, London, United Kingdom

With increasing industrialisation, London's population grew rapidly throughout the 19th and early 20th centuries, and it was for some time in the late 19th and early 20th centuries the most populous city in the world until overtaken by New York in 1925. Its population peaked at 8,615,245 in 1939 immediately before the outbreak of the Second World War. There were an estimated 7,556,900 official residents in Greater London as of mid-2007.
However, London's continuous urban area extends beyond the borders of Greater London and was home to 8,278,251 people in 2001, while its wider metropolitan area has a population of between 12 and 14 million depending on the definition used. According to Eurostat, London is the most populous city and metropolitan area of the European Union and the second most populous in Europe (or third if Istanbul is included). During the period 1991–2001 a net 726,000 immigrants arrived in London.
The region covers an area of 1,579 square kilometres (610 sq mi). The population density is 4,542 inhabitants per square kilometre (11,760 /sq mi), more than ten times that of any other British region. In terms of population, London is the 25th largest city and the 18th largest metropolitan region in the world. It is also ranked 4th in the world in number of billionaires (United States Dollars) residing in the city. London ranks as one of the most expensive cities in the world, alongside Tokyo and Moscow.