Britain's Queen Elizabeth II looks on as guardsmen ride past on their horses outside Buckingham Palace during The Queen's Birthday Parade, "Trooping the Colour" in London on June 12, 2010. 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 Queen's actual birthday is on 21 April - she turned 84 this year - but British monarchs celebrate a second "official" birthday on a Saturday in June decided by the government, this year on June 12, culminating with the annual Trooping the Colour parade. AFP PHOTO / ADRIAN DENNIS (Photo credit should read ADRIAN DENNIS/AFP/Getty Images)