Since the mid 14th century members of the Sistern family had been burgesses of Lynn, where they held property in ‘Briggate’ (High Street).
Although himself one of the potentiores of Lynn, Sistern was returned to his first Parliament when their opponents were in power. But he was possibly of moderate persuasion, for not only was he chosen as one of the 18 arbitrators in the conflict over the constitution of the town, but was also an elector of two inferiores to the first Parliament of Henry V’s reign (May 1413). Nothing more is recorded about him until, at a general meeting of the burgesses on 22 Mar. 1419, he sought to be released from his post as churchwarden in the parish of St. Margaret, having received no assistance for urgently needed repairs to the belfry and refusing to be personally liable for the cost. It was when borough coroner that Sistern was elected to Parliament for a second time (May 1421), on which occasion he himself attested the indenture of return. He was then a member of the council of 24.
