Crowds have gathered in central London for the Trooping the Colour ceremony to mark the King's official birthday.
The parade is one of the biggest royal and military spectacles of the year, culminating with a Red Arrows flypast watched by the royals from the Buckingham Palace balcony.
Alongside the King and Queen were the Prince and Princess of Wales with their children. Prince Louis has, at times, been a scene-stealer but the gap-toothed, eight-year-old was on his best behaviour, chatting to his parents as the aircraft flew overhead.
The balcony moment remains a reminder of royal continuity, with King Charles standing with two future monarchs in Prince William and Prince George.
In bright sunshine, the King and Queen travelled in an open-top carriage, driving past the thousands of people lining the route from Buckingham Palace down The Mall to Horse Guards Parade.
The title Trooping the Colour comes from the "Colours" - the name given to the flags representing the different regiments in the British Army.
It features more than 1,400 members of the armed forces as well as 200 horses and 400 musicians,
Each year, a different regiment's colours are trooped, with this year's being the Grenadier Guards.
Travelling in the first carriage were the Duchess of Edinburgh, wife of the Duke of Edinburgh, and Vice-Admiral Sir Tim Laurence, husband of the Princess Royal.
The second carriage included the Duke of Gloucester, first cousin to Queen Elizabeth II, and his wife, the Duchess of Gloucester.
On horseback, in the military parade in formation with two other royal colonels, were the Prince of Wales, the Princess Royal and the Duke of Edinburgh, while the Princess of Wales followed in a carriage with her three children.
The King wore the uniform of the Grenadier Guards featuring the cypher of Queen Elizabeth II. He also wore a number of medals such as Queen Elizabeth II's Coronation Medal (1953) to the Platinum Jubilee Medal (2022).
Queen Camilla is Colonel of the Grenadiers, replacing Andrew Mountbatten-Windsor after he gave up his military affiliations and patronages in 2022.
The Queen wore a red Grenadier Guards uniform dress designed by Fiona Clarke with a black beret with a white plume and a Grenadier Guards cap badge designed by Phillip Treacy.
Second Lt, Alec Goschen, was the Ensign, the soldier who carried the flag of the Grenadier Guards on Horseguards. He was easy to spot standing 6ft 7ins tall but reached the heights of 8ft 6ins in his bearskin.
After the parade, the King was greeted by a royal salute and a 41-gun salute fired by The King's Troop Royal Horse Artillery.
He then conducted an inspection of the troops and the colour of the regiment was then "trooped", or carried, through the ranks of foot guards.
The King led his guards back to Buckingham Palace where a further salute took place.
There was some sadness for the armed forces taking part.
Lance Bombardier Ciara Sullivan should been riding this year in Trooping the Colour. But she died after falling from her horse during the Royal Windsor Horse Show in May.
In recent weeks, soldiers of the King's Troop Royal Horse Artillery have paid tribute to her during a number of events and preparations for Saturday.
The flypast was watched by members of the Royal Family from the balcony at Buckingham Palace, in a historic occasion for the Red Arrows.
In May, it was announced that the Red Arrows, officially known as the Royal Air Force Aerobatic Team, would begin flying with fewer aircraft for the majority of their displays in a bid to preserve the ageing fleet.
However, the nine-aircraft formation have been preserved for the events on Saturday as well as next month's 250th anniversary of the US.
After that, the Red Arrows will fly with only seven aircraft.
King Charles and Queen Camilla rode in an Ascot Landau carriage, which was purchased during the reign of Queen Victoria.
For royal watchers, Trooping the Colour is rich pickings. With no jubilees, no big royal weddings nor any major national celebrations on the horizon, the parade is a key moment in the royal year.
Corrigan Gommenginger travelled from Seattle in the US to see Trooping the Colour taking up his spot on The Mall at 4am.
"I love the Royal Family," he said. "They do great things for the country. They do good things for humanity and for the world."
And closer to home, eight-year-old Sophie Moore from Letchworth in Hertfordshire, won a ballot to represent Hertfordshire Brownies at the event.
"She's so excited to see the King and the Royal Family," her father Aidan said. "It's her first experience of marching bands and she is loving the ceremony."
Anti-monarchy protesters from the campaign group, Republic, were also in the crowd, demonstrating along The Mall. They were especially noisy as the royal carriage procession passed shouting "Down with the Crown" and "You are not our King," and held up images of Andrew Mountbatten Windsor.
Trooping the Colour is a celebration of the King's official birthday. King Charles's actual birthday is 14th November but monarchs have historically also marked an official birthday for public events held in the summer when the weather is generally better.
The emphasis at this event is always on military precision and royal unity which is most obviously on show during the balcony moment.
