High Quality Content by WIKIPEDIA articles! Keith Sinjohn Joseph, Baron Joseph, Bt, CH, PC (17 January 1918 – 10 December 1994), was a British barrister and politician. A member of the Conservative Party, he served in the Cabinet under three Prime Ministers (Harold Macmillan, Edward Heath and Margaret Thatcher), and is widely regarded to have been the "power behind the throne" in the creation of what came to be known as "Thatcherism". He was known for most of his political life as Sir Keith Joseph, 2nd Baronet.