Duke was defeated at Honiton in 1754, and returned in 1761 after a contest; in 1761 he also contested Ashburton. In Bute’s list he was classed as a Tory, but was sent Newcastle’s whip for the session of 1761. He appears in Fox’s list of Members favourable to the peace preliminaries, and voted with the Grenville Administration on general warrants, 6 and 18 Feb. 1764.1In the Grenville mss (JM) there is a paper by Duke, apparently intended as a letter to his constituents, justifying his vote in the division of 18 Feb. 1764. Rockingham in July 1765 classed him as ‘doubtful’, in November 1766 as ‘Swiss’ (prepared to support every Administration), and Townshend in January 1767 as ‘doubtful’. His only other known vote was against the Chatham Administration on the land tax, 27 Feb. 1767. There is no record of his having spoken in the House. He was defeated at Honiton in 1768.
He died 3 Nov. 1775, aged 58.2Devon Cornw. N Q. xiv. 293.