Over the course of her 70-year-reign, Britain's Queen Elizabeth II met with 15 prime ministers. The queen's constitutional role involved inviting prime ministers to form a government. From Winston Churchill to Liz Truss, we look back at all the prime ministers.

Queen Elizabeth II poses with former British premiers at London's 10 Downing Street, Dec. 4, 1985, to celebrate the 250th anniversary of the British prime minister's London residence. From left, James Callaghan, Alec Douglas-Home, Harold Macmillan, Harold Wilson and Edward Heath.
Pool via AP