Sir John Thomas Duckworth, Bart., Governor of Newfoundland was born on 28 February 28, at Leatherhead, Surrey, where his father was curate. He was one of five sons and two daughters of the Reverend Henry Duckworth (1712-1794) of Middleton, Lancashire (later, vicar of Stoke Poges and rector of Fulmer, Buckinghamshire, and a minor canon of Windsor), by his wife Sarah, née Johnson (d. 1780) of Ickenham in Uxbridge, Middlesex.
He left Eton at the age of 11 to enter the Royal Navy as a midshipman, 20 February 1759, in H.M.S. NAMUR, under the aegis of Admiral Boscawen. He obtained his lieutenancy, 14 November 1771, and was promoted Commander, 21 July 1779; Post Captain, 16 June 1780; Rear-Admiral of the White, 14 February 1799; Rear-Admiral of the Red, 1 January 1801; Vice-Admiral of the Blue, 23 April 1804; Vice-Admiral of the White, 9 November 1805; Vice-Admiral of the Red, 28 April 1808; Admiral of the Blue, 31 July 1810; and Admiral of the White, 4 December 1813.
His distinguished, though somewhat controversial, career began with his taking part in the battles of Lagos Bay and Quiberon Bay in 1759. His first period of American service began at Rhode Island in 1777, when he was first lieutenant in the DIAMOND frigate, and his later service included several appointments in, and visits to, the West Indies prior to his final years in Newfoundland.
Notable events in his career include his taking part, as Captain in the ORION, in the action off Ushant, 1 June 1794, for which he was officially mentioned by Admiral Howe; his blockade of Cadiz in 1800, which included the capture of a large Spanish convoy from which he profited greatly; his taking of St. Thomas and other Swedish and Danish islands in the West Indies in 1801, for which he was made a Knight of the Bath, 6 June 1801; his complete defeat of a French fleet off Santo Domingo in 1806, for which he was rewarded by a pension of L1000 and honoured by the City of London in additioin to being presented with valuable preseents by various bodies; his forcing of the Dardanelles in 1807 in a vain attempt to carry out impossible instructions to impose terms on Constantinople; and his governorship of Newfoundland, 1810-1812, for which he received a baronetcy, 2 November 1813.
After his return from Newfoundland in 1812, he took his seat in Parliament as M.P. for (New) Romney in Kent, one of the Cinque Ports, and although he accepted the stewardship of the Chiltern Hundreds, 3 February 1813, he was again Member for that constituency at the time of his death. From January 1815 until he died, 31 August 1817, he held the appointment of Commander-in-Chief at Plymouth.
In 1776, Duckworth married Anne Wallis (d. 21 August 1797), only child of John Wallis of Trentonwoonwith, near Camelford, Cornwall. By her he had one son, Lieutenant-Colonel George Henry Duckworth (1782-1811) of the 48th Foot, who married Penelope, daughter of Captain Robert Fanshawe, R.N., and was killed at Albuera in the Peninsular War. Admiral Duckworth's daughter by this marriage, Sarah Anne Duckworth (d. 1819), married the son of Admiral Sir Richard King, who later became Vice-Admiral Sir Richard King, Bart. (1774-1834). In 1888, their son, Admiral Sir George St. Vincent King, Bart (1809-1891) assumed Duckworth's arms and prefix surname because of the failure of heirs to Sir John Thomas Buller Duckworth (b. 1809), Duckworth's son by his second marriage in 1808 to Susannah Catherine Buller (d. 1840), daughter of Dr. William Buller, Bishop of Exeter.