A son of William Dowdeswell of Pull Court, Bushley, Worcestershire, M.P. and Sheriff of Worcestershire and of Anne Hammond . He was educated at Westminster School, at Christ Church College, Oxford, then at the University of Leyden wher he had as classmates Charles Townshend (1726-1767) hand John Wilkes (1727-1797). MP for the family borough of Tewkesbury in 1747, he retained this seat until 1754, and from 1761 until his death in Nice.
He married Bridget Codrington, dau. of Sir William Codrington 1st Bart.
A prominent Whig, he became Chancellor of the Exchequer in 1765 for a brief period under the Marquess of Rockingham. He was succeeded by Charles Townshend.
Dowdeswell and other prominent Whig's position on the American crisis is discussed by York, Neil, (2005) William Dowdeswell and the American Crisis, 1763–1775.History 90 (300), 507-531. Part of his political correspondance are now at the William L. Clements Library, The University of Michigan.
His son Thomas Dowdeswell, of Pull Court (d.1811) has also a fine bookplate - F8958 - a Trophy Armorial, engraved by Moses Mordecai. The latter's wife Magdelena Pasley, dau. of Admiral Sir Thomas Pasley, Bart., also had bookplates referred in Frank's (F8955 & 8956).
His third son General William Dowdeswell (1761-1828) , Commander-in-Chief in India (1807- 1810) and governor of the Bahamas (1797-1801) was famous for his collection of English prints, which were sold in 1821. He also had a bookplate (F8959).