Frosty
Logical and sensible but turns women gay
I am quite surprised nobody has mentioned Herbert Asquith - you can talk about Clement Atlee as much as you like but it was Asquith who began building the welfare state and launched a suicide mission to change the constitution in order to make it happen, which resulted in the Parliament Act 1911, the primacy of the House of Commons ever since, and the first social protection this country has ever seen.
Passing the Parliament Act was a huge undertaking, overcoming the Lords during the Edwardian Era and political battles with the King in the process was no mean feat.
His many affairs with teenagers disqualify him surely?