Britain's Queen Elizabeth wears the Imperial State Crown during the State Opening of Parliament, London, Britain, in this November 6, 2007 file photo. Queen Elizabeth celebrates her 90th birthday on April 21, 2016. (Photo by Alistair Grant/Reuters)





Britain's Queen Elizabeth accompanied by her husband Prince Philip, wipes away a tear during the formal decommissioning service for the Royal yacht HMS Britannia at Portsmouth harbour, Britain, in this December 11, 1997 file photo. (Photo by Reuters/Stringer)





Britain's Queen Elizabeth in London in this February 29, 2012 file photo. (Photo by Eddie Mulholland/Reuters)





Senior members of Britain's royal family stand on the balcony of Buckingham Palace, London, in this June 13, 2015 file photo. (Photo by Stefan Wermuth/Reuters)





U.S. President Barack Obama (2nd L) and first lady Michelle Obama (2nd R) pose with Queen Elizabeth and Prince Phillip, Duke of Edinburgh before a State Dinner at Buckingham Palace in London in this May 24, 2011 file photo. (Photo by Larry Downing/Reuters)





Britain's Queen Elizabeth travels by train to Potsdam, Germany, in this November 3, 2004 file photo. (Photo by Ian Jones/Reuters)





Britain's Queen Elizabeth attends a service at St Paul's Cathedral in London in this March 7, 2012 file photo. (Photo by Geoff Pugh/Reuters)





Britain's Queen Elizabeth rides her horse in the grounds of Windsor Castle, three days after the death of her mother, in this April 2, 2002 file photo. (Photo by Dan Chung/Reuters)





Britain's Queen Elizabeth attends the annual Remembrance Sunday ceremony in central London November in this 14, 2010 file photo. (Photo by Stefan Wermuth/Reuters)





Britain's Prince Charles kisses the hand of his mother, Queen Elizabeth, during a visit to the Chelsea Flower Show in London in this May 18, 2009 file photo. (Photo by Sang Tan/Reuters)





Members of Britain's royal family (front L-R) Prince Philip, Queen Elizabeth and Prince Charles cheer during the Braemar Gathering in Braemar, Scotland in this September 1, 2012 file photo. (Photo by Russell Cheyne/Reuters)





Britain's Queen Elizabeth leaves the Houses of Parliament after delivering her speech in London, in this November 18, 2009 file photo. (Photo by Toby Melville/Reuters)





Britain's Queen Elizabeth looks at a corgi dog as television presenter Paul O'Grady (2nd R) smiles during a visit to Battersea Dogs & Cats Home in London in this March 17, 2015 file photo. (Photo by Ben Stansall/Reuters)





Britain's Queen Elizabeth walks behind her mother's coffin following the Queen Mother's funeral at Westminster Abbey in London, in this April 9, 2002 file photo. (Photo by Dan Chung/Reuters)





Britain's Queen Elizabeth and the Duke of Edinburgh look at floral tributes laid outside Buckingham Palace in memory of Diana, Princess of Wales, London, in this September 5, 1997 file photo. (Photo by Ian Waldie/Reuters)





Britain's Queen Elizabeth boards a train at Kings Cross station in London, in this December 17, 2009 file photo. (Photo by Stefan Rousseau/Reuters)





Britain's Queen Elizabeth (R) receives a scroll from Bruce Two Dogs Bozsum at Southwark Cathedral in London, in this November 22, 2006 file. (Photo by Stefan Rousseau/Reuters)





Britain's former Prime Minister Lady Thatcher (L) is greeted by Queen Elizabeth II (R) as she stands with Cherie Blair (2nd L) and former Prime Minister Tony Blair during a service to commemorate the 25th anniversary of the liberation of the Falkland Islands at Pangbourne College, Berkshire, Britain in this June 14, 2007 file photo. (Photo by Stephen Hird/Reuters)





Britain's Queen Elizabeth leaves Buckingham Palace in a horse drawn carriage, London in this May 25, 2010 file photo. (Photo by Suzanne Plunkett/Reuters)





Nelson Mandela and Britain's Queen Elizabeth II ride in a carriage outside Buckingham Palace, London, in this July 9, 1996 file photo. (Photo by Reuters/Stringer)





Britain's Queen Elizabeth before the State Opening of Parliament in the House of Lords, London, Britain in this May 27, 2015 file photo. (Photo by Suzanne Plunkett/Reuters)