Trenchard—whose grandfather had been an associate of the 1st Earl of Bedford as commissioner for church goods in Dorset—sat for Bridport while still in his twenties: both here and at Dorchester in the following year he was presumably brought into Parliament through the influence of the 2nd Earl of Bedford. Knight of the shire in 1584, Trenchard was named to the subsidy committee, 24 Feb. 1585. He was recommended for appointment as deputy lieutenant by the dying Earl in 1585, and was appointed that year.
Trenchard concerned himself with several Dorset boroughs, arbitrating in 1577 in a dispute at Weymouth, where he was active at various times until 1590. He intervened in a dispute at Poole in 1586, and in the same year he and Horsey wrote from Wolveton to his ‘loving friends the mayor of Poole’ and other townsmen, directing them to secure the election to Parliament of the nominee of the Earl of Warwick, ‘in consideration of the young Earl of Bedford’ his ward. Letters written from Lyme Regis in 1590 were in connexion with his duties as a piracy commissioner.
His friend Sir John Horsey died in 1589 and Trenchard, who was appointed an overseer to his will, received a ring inscribed vita brevis amicitia longa. Horsey had made his cousin Ralph his heir, and thenceforward he and Trenchard frequently acted together in local affairs. In 1593 Trenchard was host to Sir Walter Ralegh, Carew Ralegh and Horsey at the famous dinner party at Wolveton which led to a commission of inquiry into Sir Walter’s atheism. Trenchard bought Lytchett Matravers in about 1611, and thereupon resigned the recordership of Dorchester because of his distance from the town. His last years were marred by the extravagance and early death of his heir George and by an illness that confined him to the house. He died 24 Nov. 1630, appointing his second son, Thomas, executor.
