Circa 1376, Thomas joined the French in the Hundred Years' War and was imprisoned in Gloucester Castle, for treason, from 1378 to 1391.
After being released, he was allegedly considered mentally retarded, despite being appointed to "keep the seas" (with the 4th Baron Clinton and Sir Richard Waldegrave) in 1402.
He was later considered sane when examined by King Henry IV and his Council in c. 1406.
After his first wife died, he was married to Joan Brounflete (died 1409) and they had one daughter, Joan (1406–1490) who later married William Neville, Earl of Kent.
It was later called out abeyance for the Earl of Kent in right of his wife.