LONDON - June 11: Catherine, Duchess of Cambridge and Camilla, Duchess of Cornwall stand on the balcony of Buckingham Palace after the Trooping the Colour parade.

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.

Via Getty images.