Sources differ as to how Watson and the artist John Singleton Copley met in 1774: some say they travelled on the same ship from Boston to England, and some that they met in London. Whatever the circumstances of their meeting, Watson commissioned Copley to produce the work, known as Watson and the Shark which was completed in 1778. The painting was exhibited at the Royal Academy in 1778, and caused a sensation.While swimming alone in Havana harbour, Cuba, the boy was attacked by a shark. He lost his right leg below the knee in the attack, and a painting of the event still hangs in the Smithsonian in Washington. Watson walked thereafter with a crutch, but remained undaunted, distinguishing himself in the military.

By 1772, he had returned to the UK as a merchant. He was part of the original committee of Lloyd’s of London, later becoming Lloyd’s Chairman, and was the first Chairman of the Patriotic Fund, established in 1803 to help servicemen and their families.
Watson went on to become an MP for the City of London, Lord Mayor of London and eventually became a director of the Bank of England.

Watson later became a merchant, MP for the City, and Chairman of Lloyd’s in 1772. In the 1790s, he was Lord Mayor, concluding his career as a Director of the Bank of England.