A lone woman rider approaches the dais, it's her birthday, the band strikes up Hearts of Oak.
As the red jacketed soldiers move off, the crowd of spectators starts applauding, arms move in unison in time with the pace.
Boots hit the gravel with a sound like crunching cornflakes, red striped trouser seams crease as their owners march as one toward the dais.
When the first rank breasts the platform the guards commander orders "eyes left" the bear skinned heads snap round until they pass, then they snap forward again, in a rippling effect.
Brass buttons gleam in the early sun, competing with the Life Guards cuirasses as they ride towards the Queens Troop horse artillery.
Tourists cameras flash as the parade is freeze framed in a thousand lenses, sensors working hard as the high speed whine blurs the shutters.
The band now plays the Grenadiers March, the pressed crowd applauds again jostling forward to get a better view.
Row upon row of guardsmen pass the dais their officers saluting with their sabres, the dressing is superb, their legs and arms rise and drop as one, holding the line ruler straight...