Historian AJP Taylor was fascinated by the changing power of the prime minister. Recorded in the early 1960s for university lectures, here are some of his views. With Professor Peter Clarke , Master of Trinity Hall, Cambridge. 2: Pitt the Younger. Prime ministers often have to deal with barmy backbenchers but what happens when it's the king who's lost his mind? Pitt had to be careful not to drive George III out of his head and off his throne. Producer Matt Thompson Repeated from Sunday