 Nominated to be one of the High Court Judges in the trial of King Charles I of England in 1649, Barrington, although he was a family connection of Oliver Cromwell, refused to attend its meetings and declined to sign the warrant for the king's execution.From 1645 to 1648 and again from 1660 to 1679, he was a Member of Parliament (MP) for Newtown.He was a rather inactive member, due partly to his increasing ill-heath.