Lee moved to London as a mercantile agent for Virginia in the tobacco trade and there married his heiress cousin Hannah Philippa Ludwell on March 7, 1769. After joining the Haberdashers Company he was appointed Sheriff of London for 1774 when Sheriff Plomer resigned. The other sheriff for that year, Stephen Sayes, was also American born. The position gave them the opportunity to press in high places the American case for less taxation and more representation. After his year as sheriff he was elected an Alderman and continued his campaign for American rights. He served as an agent of the Continental Congress during the American Revolution, and was posted to Berlin and Vienna but forced by the political situation to take up residence in Frankfurt. He attempted, but failed, to obtain support from Austria or Prussia. An unofficial U.S.-Dutch treaty that he helped draft became the cause of the Fourth Anglo-Dutch War. Towards the end of the war he moved to Brussels, and then, leaving his wife and children there, returned to Virginia. His wife died suddenly in Ostend the following year on her way home with the children. Although ill and going blind, Lee in 1790 accepted the post of James City County sheriff in Virginia, serving two years. He died in 1795 and was buried in Jamestown, Virginia.
Personal life
William married Hannah Phillipa Ludwell on March 7, 1769, in London, following the death of her father in the same city. Hannah was the daughter of Col. Philip Ludwell III and Frances Grymes. Frances was the older sister of Lucy Grymes, who married Maj. Gen. Henry Lee II. Hannah died August 18, 1784 in Ostend, Belgium and was buried in London, England. Frances was the daughter of Hon. Charles Grymes and Frances Jennings. Charles resided at "Morattico" in Richmond Co., Virginia. Philip III was the son of Philip Ludwell, Jr. and Hannah Harrison. Philip III resided at Green Spring Plantation, Virginia. His three daughters were Hannah Philippa Ludwell, Frances, and Lucy Ludwell Paradise.
William was the son of Col. Thomas Lee, Hon. of "Stratford Hall", Westmoreland Co., Virginia. Thomas married Hannah Harrison Ludwell. Hannah was the daughter of Col. Philip Ludwell II of Green Spring Plantation, and Hannah Harrison. Thomas was the son of Col. Richard Lee II, Esq., "the scholar" and Laetitia Corbin. Laetitia was the daughter of Richard's neighbor and, Councillor, Hon. Henry Corbin, Sr. and Alice Burnham. Richard II, was the son of Col. Richard Lee I, Esq., "the immigrant" and Anne Constable. Anne was the daughter of Thomas Constable and a ward of Sir John Thoroughgood.