When his brother Gilbert died in 1202, Thomas inherited the lordship of Headington as well as land at Colyton and Whitford in Devon.
On one occasion he ate with the king when he was supposed to be fasting; as penance, he had to feed 20 paupers.
[7] Basset is notable as one of 27 ecclesiastical and secular magnates who had counselled John to accept the terms of Magna Carta in 1215 and is named in the preamble to the document; his younger brother Alan was also named among the counsellors on the charter.
[10] Basset married Philippa, daughter of William Malbank, 3rd Baron of Wich Malbank and they had three daughters:[11] Basset endowed Bicester Priory (founded by his brother Gilbert in 1183).
He died in 1220 (before October, aged about 64) and his lands were divided amongst his daughters, his will being drawn up by Peter des Roches.