London’s biggest industry is finance, and its financial exports make it a large contributor to the UK’s balance of payments. The City is the largest financial centre in London, home to banks, brokers, insurers and legal and accounting firms. A second, smaller financial district is developing at Canary Wharf to the east which includes the global headquarters of HSBC, Reuters, Barclays and the largest law firm in the world, Clifford Chance. London handled 31% of global currency transactions in 2005 — an average daily turnover of $753 billion — with more US dollars traded in London than New York, and more Euros traded there than every other city in Europe combined.

London is host to many company headquarters. More than half of the UK’s top 100 listed companies and over 100 of Europe’s 500 largest companies are headquartered in central London, and over 70% of the FTSE 100 are located within London’s metropolitan area.

Along with professional services, media companies are concentrated in London and the media distribution industry is London’s second most competitive sector. The BBC is a key employer, and other broadcasters also have headquarters around the city. Many national newspapers are edited in London, having traditionally been associated with Fleet Street in the City, but they are now primarily based around Canary Wharf. Soho is the centre of London’s post-production industry.

Tourism is one of London’s largest industries, attracting 27 million visitors every year. From once being the largest port in the world, the Port of London is now only the third-largest in the United Kingdom, handling 50 million tons of cargo each year. Most of this actually passes through Tilbury, outside the boundary of Greater London.