Britain's Prince William (L), Prince Charles (C) and the Duke of Kent ride horses as they make their way from Buckingham Palace to attend the Trooping the Colour ceremony in central London June 11, 2011. Trooping the Colour is a ceremony to honour the sovereign's official birthday. [Photo/Agencies]

Britain's Camilla, Duchess of Cornwall, Catherine, Duchess of Cambridge (C) and Prince Andrew sit in a horse drawn carriage as they make their way from Buckingham Palace to attend the Trooping the Colour ceremony in central London June 11, 2011. Trooing the Colour is a ceremony to honour the sovereign's official birthday. [Photo/Agencies]