This article reports the results of a recent survey of British Members of Parliament (N = 158) to explore parliamentary evaluations of post-war British Prime Ministers. The survey was fielded in 2013 as a part of a collaborative research project undertaken by undergraduate students. It finds that MPs in general rated Margaret Thatcher as the most successful post-war Prime Minister, with Clement Attlee a close runner-up. It also finds that MPs prioritised the implementation of party policy above merely winning elections, and that MPs thought successful Prime Ministers need to be decisive, principled and intelligent.