London CNN  — 

King Charles III revived a royal tradition by riding on horseback in the first Trooping the Colour of his reign, which marks the British sovereign’s official birthday.

The traditional military spectacle on Saturday is a parade like no other with all the pomp and pageantry expected of royal occasions, and draws massive crowds to central London. Charles’ actual birthday is in November and is typically celebrated privately.

He joined 1,500 soldiers, 300 horses and hundreds of musicians as they filed the short distance from Buckingham Palace to Horse Guards Parade in St James’s Park for the ceremony watched by members of the royal family.

It was a sight not seen for nearly 40 years. The last time a reigning monarch rode in the procession was Queen Elizabeth II in 1986.

King Charles donned a Welsh Guard uniform, with leek emblem on the collar and green and white plum on his bearskin, for the occasion.

He was followed on horseback by several royal colonels including Prince William, also wearing a uniform of the Welsh Guard, the regiment he inherited from his father in December. He rode alongside Princess Anne, Gold Stick in Waiting and Colonel of the Blues and Royals, and Prince Edward, who is Colonel of the London Guards.

Since 1748, Trooping the Colour has marked the official birthday of the British Sovereign.

Behind them was a horse-drawn carriage carrying the Queen, Catherine, Princess of Wales and the crowd-pleasing trio of Prince George, Princess Charlotte and Prince Louis. The royal party was accompanied by a Sovereign’s Mounted Escort of soldiers from the Household Cavalry’s Life Guards and Blues and Royals.

Kate appeared to nod to her ceremonial role as Colonel of the Irish Guard through her choice of outfit, a resplendent green ensemble. Meanwhile Queen Camilla was dressed in honor of the Grenadier Guards, the regiment she was named colonel of in January, according to the Palace.

She wore a red silk coat dress “with the rank insignia of a full colonel on the epaulettes. The dress incorporates key details from the uniform including the ‘The Grenade Fired Proper’ embroidered in gold bullion on the collar and the gold bullion back slashes,” it said.

The queen consort completed the look with a hat by London milliner Philip Treacy “which is a nod to the bearskin with a ‘Grenade’ exploding up to a feather plume.”

Queen Camilla, left, and Catherine, Princess of Wales greet crowds outside Buckingham Palace.
The King's grandchildren, Princes George and Louis and their sister, Princess Charlotte, ride in a horse-drawn carriage to the parade ground.

Well-wishers dressed in fascinators and draped in Union flags had gathered early to claim prime positions along the Mall outside the royal residence in the hours ahead of the parade.

By the time the ceremonial spectacle began, thousands were waiting in the summer sunshine. A cascade of enthusiastic cheering could be heard as the royals processed down the Mall for the short journey to the parade ground. Many held their cell phones aloft to capture the moment family members passed by.

Bidisha Mamata, broadcaster and royal watcher, told CNN there was “a real sense of celebration.”

“The coronation was very serious … there was a lot of medieval pageantry. This is much more military focused. This is so much more about connecting King Charles with his own history in the Marines, the RAF - he has a strong connection to the military,” she said.

The monarch is head of Britain’s armed forces and would traditionally lead an army into war. During the ceremony at Horse Guards, the monarch took the salute as Colonel in Chief of the Household Division’s seven regiments as the national anthem played. He was then given a chance to review and approve his army.

Around 1,500 soldiers, 300 horses hundreds of musicians participated in the King's birthday parade.
Members of the Welsh Guards perform on Horse Guards Parade.

Queen Camilla joined her husband to watch the 1st Battalion Welsh Guards troop their color, or regimental flag, in front of hundreds of Guardsmen and officers. The regiment carried out intricate battlefield drill maneuvers to music, with Kensington Palace previously describing this year’s musical program as having “a distinctly Welsh theme,” with new compositions from the band specially for the occasion.

After the parade, the royal party returned to Buckingham Palace along the same route. There they made a balcony appearance to watch an extended military flypast and greet a sea of royal supporters. A similar display had to be scaled back after the King’s coronation last month because of poor weather.

The King was joined on the balcony by working members of the royal family and their children. William and Kate’s children clearly enjoyed the aerial display, pointing up as the aircraft blazed overhead.

The Red Arrows fly in formation over Buckingham Palace.