During the 19th century a glamorous coterie of American bankers, socialites, and artists frequented the capital. In 1936 the King of England abdicated in order to marry American divorcee Wallace Simpson.
World Wars I and II saw London thronging with American troops. But it was during the postwar period that American culture had its biggest impact on the lifestyles of ordinary Londoners.
Americans have been present in London since the visit of the Virginian Princess Pocahontas in 1616.
Most have eventually returned to America, but their influence on the development of the capital has been considerable.
In the 19th century the American community was always several thousand strong. Its members included financiers such as George Peabody and J. P. Morgan, entrepreneurs like Gordon Selfridge and heiresses including the future mother of Winston Churchill.
Amongst the numerous writers and artists were Henry James, John Singer Sargent and James Abbott McNeill Whistler, as well as a succession of entertainers.
The majority of Americans in London were employed in American businesses, particularly those involved in engineering, manufacturing, office equipment and banking.
Black Americans, from fugitive slaves to actors and dancers, also came to London. By the turn of the 20th century there were up to 20,000 Americans in the capital, supporting a variety of clubs and newspapers.
In 1936, King Edward VIII abdicated the throne to marry the American divorcee Wallis Simpson. The event caused a huge scandal.
During both world wars, while most American civilians went home, large numbers of American troops came to London. One was General Eisenhower, Supreme Commander of the Allied Forces in Europe. During World War II, the Grosvenor Square area became known as 'Eisenhower Platz'.
US influence on business, media, music and fashion has been especially strong since the second half of the 20th century.
Half of all international businesses in London are American, totalling around 6,700 US-owned companies. They are primarily in the finance and business services sector and located in the City or Canary Wharf.
There are currently 45,000 Americans and 15,000 Canadians living in the capital. Their homes are in well-heeled boroughs such as Kensington and Chelsea or Westminster.
Americans are London's most frequent foreign visitors, while thousands of American students enrol on degree courses at London universities each year.
The American Church in London, located in Tottenham Court Road, caters to this group's religious needs. The Eccles Centre for American Studies at the British Library holds the largest collection of American printed material outside the US.
Famous American inhabitants of London currently include Gwyneth Paltrow and Kevin Spacey, now director of the Old Vic theatre.