Background
He was born on 30 March 1649 at Lytchett Matravers, near Poole, to Thomas Trenchard of Wolverton (1615–1671), and his wife Hannah née Henley.
He was born on 30 March 1649 at Lytchett Matravers, near Poole, to Thomas Trenchard of Wolverton (1615–1671), and his wife Hannah née Henley.
He was educated at Winchester (1661-1665) and at New College, Oxford (1665-1667).
John Trenchard entered parliament as member for Taunton in 1679, and associated himself with those who proposed to exclude the duke of York from the throne. He attended some of the meetings held by these malcontents and was possibly concerned in the Rye House plot; at all events he was arrested in July 1683, but no definite evidence was brought against him and he was released. When Monmouth landed in the west of England in June 1685 Trenchard fled from England, but was pardoned through the good offices of William Penn and returned home two years later. Again he entered parliament, but he took no active part in the Revolution of 1688, although he managed to secure the good will of William III. He was made chief justice of Chester, and in 1692 he was appointed a secretary of state. He and the government incurred much ridicule through their failure to prove the existence of a great Jacobite plot in Lancashire and Cheshire in which they had been led to believe. Sir John died on the 27th of April 1695.
On 10 November 1682, he married Philippa Speke, daughter of George Speke of White Lackington, Somerset, with 4 sons and 3 daughters.