London is considered to be the worlds number one city for global finance and has Alpha++ status on the Global City index (a city which is a major node in the global economic network because of its strong influence in the arts, commerce, design, education, entertainment, fashion, finance, health-care, media, research and tourism).
In terms of of GDP, it has the second-largest economy (2018) among European cities after Paris (No 1) and before Milan (No 3).
Much of London's finance industry is located at the "Square Mile" the long standing business hub of London. The other major financial district is Canary Wharf, which is about 4Km east of the City just before the O2 Arena in Greenwich and slightly north of the Isle of Dogs.
Both these financial districts have seem massive growth, and due to property planning restrictions, Canary Wharf is now the best choice for most new firms. It has been estimated that financial services employs about 315,200 people within the City.
London also thrives as a centre for insurance, foreign exchange and bond trading. The city has many trading facilities and hubs dealing in foreign exchange, futures, global insurance and bonds. The Bank for International Settlements estimates that London generates £88 Billion (46%) of daily global revenue in the interest-rate derivative market.
(C) 2018 ~ 2020 Theia - Stats