Poynings was enrolled at
Gray's Inn in 1533. His military service began during the Boulogne campaign of 1546. His brother, Edward, captain of the guard at Boulogne, was killed in action in January, and replaced by
Thomas Wyatt, whose lieutenant Poynings became in February. In June 1546 he was appointed captain of the citadel at Boulogne, and a year later, captain of the town. His nephew,
Lord Clinton, became governor of Boulogne in 1548, and Poynings continued to serve there until the town was returned to the French in 1550. In 1552, he was appointed lieutenant of the castle of
Calais, and, in 1557, was present, with 48-foot soldiers, at the
Battle of St. Quentin. He was knighted by
Queen Elizabeth no later than 1562, and was Member of Parliament for
Tregony in 1559. On 1 December 1560, he was appointed captain of
Portsmouth, a position he held until his death. During the English occupation of
Le Havre, then known to the English as Newhaven, in 1562, he was appointed high marshal, and since the overall commander,
Ambrose Dudley, 3rd Earl of Warwick, 'lacked experience, he was directed by the privy council to be instructed by his marshal'. Poynings' orders for the conduct of the English forces at Newhaven included strictures such as
"Any English who shall draw his weapon or fight without the town shall lose his right hand. Any soldier that gives a blow within the town shall lose his hand." In late November 1562,
Sir Hugh Paulet replaced Poynings at Newhaven, although he continued to serve on the military council. On 25 March 1563, he was directed to return to London to report to the
Privy Council, and while he was there, the garrison at Newhaven under Warwick surrendered on 27 July. As a reward for his services he was granted
denization in 1564. Poynings' wife, Mary West, was coheir to the barony of West after the death of her half-brother,
Thomas West, 9th Baron De La Warr, and eventually sole heiress to her sister, Anne West. In 1567, Poynings unsuccessfully claimed the other title held by the West family, the barony of De La Warr, in right of his wife. Poynings' final years were spent as captain at
Portsmouth, where he is said to have quarrelled with the mayor and burgesses, 'who accused him of high-handedness and violence'. ==Death==