Queen Elizabeth II's 12 prime ministers
During her 64-year reign, Queen Elizabeth II has been served by 12 prime ministers. Many relationships were formed -- from Winston Churchill, to "Iron Lady" Margaret Thatcher -- and some proved more difficult than others. While most of their political and personal conversations are kept strictly confidential, memoirs and historic interactions provide an insight into their relationships. So as Theresa May becomes Britain's next Prime Minister -- and Her Majesty's 13th -- take a look back at those who have served her.