In this Tuesday, June 8, 1982 file photo, U.S. President Ronald Reagan, left, on Centennial, and Britain's Queen Elizabeth II, on Burmese, go horseback riding in the grounds of Windsor Castle, England. Britain's Queen Elizabeth celebrates her 90th birthday on Thursday, April 21, 2016. (AP Photo/Bob Daugherty, file)
Britain's Queen Elizabeth II stands in the grounds of Balmoral Castle, Scotland, with U.S. President Eisenhower, Aug. 29, 1959. From left to right, Prince Philip, Princess Anne, President Eisenhower, Queen Elizabeth II and Prince Charles. (AP Photo).