He moved to London as an iron merchant and by 1800 was senior partner in the firm of Thompson, Forman and Homfray of Bankside, which had interests in iron manufacturing. He became master of the Ironmongers’ Company in 1829 and 1841 and was elected an Alderman for life in 1821, Sheriff of the City of London for 1822–1823 and Lord Mayor of London for 1828–29.
He served as Chairman of Lloyds of London (1826-33), treasurer (1826–29), vice-president (1829–43) and president (1843–54) of the Honourable Artillery Company and a director of the Bank of England from 1827 to his death. Other public offices included treasurer of King’s College, London (1828 to his death), president of Christ’s Hospital (1829 to his death), trustee of the Patriotic Fund (1833 to his death) and deputy-chairman (1848–51) and chairman (1851 to his death) of the St. Katharine’s Dock Company.
He also served as Lieutenant-colonel of the London Militia (1835-51) and colonel from 1851 to his death.
- D. R. Fisher, ed. (2009). "THOMPSON, William (1792-1854), of Dyer's Hall Wharf, Upper Thames Street, London and 12 Gloucester Place, Mdx". The History of Parliament. Retrieved 27 November 2019.