A Royal Navy officer fainted just moments before taking part in the procession heading back to Buckingham Palace for the King's Coronation.
A small number of troops rushed to assist their colleague who was quickly put onto a stretcher and given medical assistance.
More than 4,000 ceremonial troops took part in the procession, which began at 1.07pm, to escort the King and Queen back to Buckingham Palace in the Gold State Coach.