Desc: From Churchill to Truss: The Queen's Prime Ministers: Directed by Sarah Findley. With Tony Blair, Gordon Brown, James Callaghan, David Cameron. From war to strikes, Brexit to Westminster scandals, Queen Elizabeth II witnessed vast changes over the course of her 70 year reign. As the longest reigning Monarch in British history, Her Majesty the Queen worked with a record fifteen Prime Ministers, forming a unique relationship with each and every one. Prime Ministers came and went, but the late Queen remained a figure of calm and constancy during periods of political turmoil and division.