Trooping the Colour in London
Marking the British monarch's official birthday each June, Trooping the Colour sees Household Division regiments perform precise ceremonial drill on Horse Guards Parade before a royal procession along the Mall, ending with a Buckingham Palace balcony appearance and Royal Air Force flypast that draws the year's largest single-day crowds to the area.
Trooping the Colour dates back to a practical military need in the eighteenth century: soldiers needed to recognize their own regiment's flag, or colour, in the chaos of battle, so regiments would ceremonially parade, or troop, the flag in front of the assembled ranks so it stuck in memory.