The King will become the first monarch in more than 30 years to take part in Trooping the Colour on horseback this morning.
Charles will take the royal salute as Colonel in Chief of the Household Division’s seven regiments during the ceremony, staged on Horse Guards Parade, as members of the Royal Family and 8,000 spectators look on.
The colour, or regimental flag, that will be trooped in front of hundreds of Guardsmen and officers will be the King’s Colour of the 1st Battalion Welsh Guards.
He will be the first monarch to ride during the official birthday celebration since his mother, Queen Elizabeth, rode her horse named Burmese during the ceremony in 1986.
Burmese, a gift from the Royal Canadian Mounted Police, was the Queen’s favourite mount for ceremonial occasions and she rode her for 18 years until the mare’s retirement in 1986.
From that point on, Her Majesty opted to use a carriage for Trooping the Colour rather than train another charger.
When the King rides from Buckingham Palace to Horse Guards, he will be joined on horseback by the royal Colonels – Prince of Wales, Colonel, Welsh Guards and the Princess Royal, Gold Stick in Waiting and Colonel, The Blues and Royals.
The Duke of Edinburgh will also be riding during the ceremony in his role as Colonel of the 1st Battalion London Guards, formed last year.
The senior royals on horseback will be joined by a carriage expected to be carrying the Queen and the Princess of Wales and her children.
The royal party will travel in the middle of a Sovereign’s Mounted Escort formed by troops from the Household Cavalry’s Life Guards and Blues and Royals, with two divisions riding in front and two behind.
During the Trooping ceremony, the King will inspect the Guardsmen, in their scarlet tunics and bearskins, standing in two rows on Horse Guards before the colour is trooped.
The massed bands of the Household Division will provide musical backing during the day and also taking part is the King’s Troop Royal Horse Artillery who, following the parade, will fire a 41-gun salute in Green Park to mark the King’s official birthday – while from the Tower of London the Honourable Artillery Company will fire 62 volleys.
Following the ceremony, the Royal Family will head back to Buckingham Palace and gather on the balcony to watch an extended military flypast after the display on coronation day had to be scaled down due to bad weather.
Around 70 aircraft from the Royal Navy, British Army and Royal Air Force will take part – including aircraft from the Battle of Britain Memorial Flight, the C-130 Hercules on its final ceremonial flight, modern Typhoon fighter jets with a red, white and blue finale from the Red Arrows.