during the english civil war he was a staunch royalist, who attempted to raise welsh troops for the royalist cause, leading to his ejection from the university in 1648. he retired to glamorgan, as did his protege (and successor as principal of jesus) leoline jenkins. they both took refuge at the house of sir john aubrey, first of the aubrey baronets, at llantrithyd, as did gilbert sheldon, the future archbishop of canterbury. both mansell and jenkins remained there until 1651, when parliament ejected jenkins for running a "seditious academy" (in fact a private boys school), and both he and mansell returned to oxford. here, due to the respect in which he was universally held, mansell was given rooms in his old college. he was left in peace, and at the restoration of charles ii briefly resumed the office of principal, but due to his failing eyesight he resigned a year later in favour of jenkins.