he was born at muddlescombe, carmarthenshire, the third son of sir francis mansel (died 1628), first of the mansel baronets, and his first wife catherine morgan. he was educated at the free school in hereford and then at jesus college, graduating bachelor of arts in 1611. he became doctor of divinity in 1624. his election as principal of jesus college in 1620 was in the face of strong opposition, and he apparently thought it prudent to resign a year later and wait for a more favourable opportunity. his re-election in 1630 following the death of his successor eubele thelwall seems to have been uncontroversial.