Britain's King Charles III (3R) salutes as members of the Blues and Royals return, outside Buckingham Palace after the King's Birthday Parade, 'Trooping the Colour', in London, United Kingdom on Saturday. The ceremony of Trooping the Colour is believed to have first been performed during the reign of King Charles II. Since 1748, the Trooping of the Colour has marked the official birthday of the British Sovereign. Over 1500 parading soldiers and almost 300 horses took part in the event.