Trenchard’s ancestors held manorial property in Hampshire from the twelfth century. One of the family represented that county in the 1449 Parliament, but subsequently settled in Dorset after marrying the heiress to the Wolveton estate.21 VCH Hants, v. 112; OR; Hutchins, iii. 326. Trenchard’s father, Sir George senior, was one of the county’s most prominent gentlemen during the final decades of Elizabeth’s reign, and the first of the family to sit regularly in Parliament. One of Trenchard’s elder brothers died young; the other, Sir George junior, was a wastrel who died heavily in debt in 1610.22 HP Commons, 1558-1603, iii. 526-7; Harl. 1579, f. 132. Nevertheless, Sir George senior remained a highly influential local figure, and Trenchard was returned unopposed to the third Jacobean Parliament as a Dorset shire knight, along with his brother-in-law Sir John Strangways*. Trenchard is not known to have spoken in the Commons, and his only appointment was to attend a conference with the Lords on the joint petition about recusancy (15 Feb. 1621). He did not stand again until after his father’s death in 1630.23 Hutchins, iii. 326; CJ, i. 522b.
According to the 1st earl of Shaftesbury (Sir Anthony Ashley Cooper†), Trenchard was ‘a very honest, well-natured, worthy man, a favourer of the puritans’.24 W.D. Christie, Life of Shaftesbury, i. app. 1, p. xix. His term as sheriff of Dorset coincided with the introduction of Ship Money, which he was broadly successful in collecting.25 M.D. Gordon, ‘Collection of Ship Money in the Reign of Chas. I’, TRHS (ser. 3), iv. 155, 157; CSP Dom. 1635-6, pp. 211-12, 356. A supporter of Parliament during the Civil War, he returned to the Commons in 1645 as a recruiter, but was secluded at Pride’s Purge.26 D. Underdown, Pride’s Purge, 387. Trenchard died in about 1652, intestate and heavily indebted. His son Thomas sat for Bridport in the Short Parliament, and his grandson Thomas was elected for Poole in 1670.27 Alnwick, Northumberland ms 551, f. 142.