The Queen has taken to an open-top vehicle to inspect a ceremonial military unit which owes its existence to her father King George VI.
Standing in a state review Land Rover, the Queen was driven past the massed ranks of the King's Troop Royal Artillery - formed in October 1947 at the request of the King who wanted a troop of horse artillery to take part in the great ceremonies of state.
The Troop are famed for firing gun salutes on royal anniversaries and state occasions, and for providing a gun carriage and a team of black horses for state and military funerals.
Equipped with 13-pounder field guns dating from the First World War, the soldiers are superb equestrians who, when not performing ceremonial duties, can be deployed around the world on operations.
After inspecting the ceremonial unit, the Queen took her place on a dias in Hyde Park to receive the royal salute of the servicemen and women as their guns and horses thundered past.
The King had requested the Troop be formed in the post-war period as the last batteries of horse drawn artillery were being mechanised and in October 1947 he inspected the new unit.
When signing the visitors' book after the ceremony George famously crossed out the unit's old name of Riding and inserted above it King's, so it read King's Troop, Royal Horse Artillery.