Britain's Queen Elizabeth II (front CL) and her husband Prince Philip, Duke of Edinburgh (front CR) wave as they stand on the balcony of Buckingham Palace with (L-R) Britain's Princess Anne, Princess Royal, Camilla, Duchess of Cornwall, Prince Charles, Prince of Wales, Prince William, Duke of Cambridge holding his son Prince George of Cambridge, Catherine, Duchess of Cambridge (back), Prince Harry, James, Viscount Severn, Prince Andrew, Duke of York (back), Princess Beatrice of York, Lady Louise Windsor, Princess Eugenie of York at the end of the Queen's Birthday Parade, 'Trooping the Colour,' in London on June 13, 2015. The ceremony of Trooping the Colour is believed to have first been performed during the reign of King Charles II. In 1748, it was decided that the parade would be used to mark the official birthday of the Sovereign. More than 600 guardsmen and cavalry make up the parade, a celebration of the Sovereign's official birthday, although the Queen's actual birthday is on 21 April.  AFP PHOTO / BEN STANSALL        (Photo credit should read BEN STANSALL/AFP/Getty Images)