All eyes were on the Prince and Princess of Wales youngest child Louis, who is famed for his antics on big royal occasions.
The King’s official birthday celebrations were topped with a Red Arrows fly-past as Prince Louis appeared eager to see his grandfather.
Charles’ anniversary was celebrated with a display of military pomp and pageantry that showcased the best of the Army’s ceremonial prowess on Horse Guards Parade in front of the royal family and thousands of spectators.
All eyes were on the Prince and Princess of Wales youngest child Louis, who is famed for his antics on big royal occasions, and he was spotted ducking down to look through a half-open window to catch a glimpse of Trooping the Colour.
The eight-year-old prince was watching events from the first-floor window of the Duke of Wellington’s former office with siblings Prince George, 12 and Princess Charlotte, 11, and other royals including the Duchess of Edinburgh and Vice Admiral Sir Tim Laurence.
Below in the parade ground on a royal dais were the King, Queen and Kate, who wore a striking wide-brimmed blue and white Philip Treacy hat and matching Catherine Walker outfit.
The royal women paid tribute to their regiments, with Kate sporting the brooch of the Irish Guards, of which she serves as Colonel, while Camilla is Colonel of the Grenadier Guards and wore a red Fiona Clare dress based on their uniform and a black beret with white plume by Treacy, featuring her regimental cap badge.
Trooping the Colour is a historic ceremony where colours, or regimental flags, used as rallying points in battle were “trooped” or paraded in front of soldiers so they would be recognised, leading to them taking on great symbolic importance as the heart and soul of a regiment.
The ceremony evolved into a celebration of the head of state’s official birthday and this year the colour trooped was the King’s Colour of the Grenadier Guards, presented by the King earlier this week during a Buckingham Palace ceremony.
Trooping is as much a social occasion as a ceremonial event and stands around Horse Guards Parade were filled with about 8,000 family members of the guards and officers on parade.
In summer sunshine, Charles inspected the troops from a carriage, passing the ranks of just over a thousand guardsmen from the Grenadier, Scots, Irish and Coldstream Guards regiments and later stood to salute as the colours were marched past him, first slow then in quick time by the servicemen.
The national celebration is one of the highlights of the royal calendar.
The Duke and Duchess of Gloucester and Duke of Kent were also gathered on the Buckingham Palace balcony for the traditional fly-past of RAF aircraft.
The aerial display roared over the palace in 10 waves and featured Typhoon jets, Chinook helicopters, C-17 large military transport planes and the Red Arrows trailing their trademark red, white and blue smoke and joined by four F35-B short take-off and vertical-landing jets.
Louis was smartly dressed in a shirt, trousers, tie and double-breasted jacket for the event and at one point pulled at his collar as he tried to loosen it.
When the Red Arrows flew over he turned and spoke to his parents, making William and Kate laugh.
Crowds had gathered in The Mall to see the royal family but the area directly in front of Buckingham Palace was kept free of spectators.
Anti-monarchist group Republic staged a demonstration while the royals were on the balcony, opening umbrellas that spelled out the words “Stop The Reign”.
