FILE - British Prime Minister Theresa May curtsies as Britain's Queen Elizabeth II arrives at a ceremonial welcome for Spain's King Felipe and Queen Letizia on Horse Guards Parade in London, Wednesday, July 12, 2017. In seven decades on the throne, Queen Elizabeth II saw 15 British prime ministers come and go, from Winston Churchill to Margaret Thatcher to Boris Johnson to Liz Truss. (AP Photo/Matt Dunham, Pool, File)