King Charles may arrive in a carriage rather than on horseback but his attendance at Saturday’s Trooping the Colour was “non-negotiable,” according to sources who are arranging the ceremony.

Highlights From Trooping the Colour

The king will inspect the soldiers from a carriage with Queen Camilla at Horse Guards Parade before returning to Buckingham Palace to lead the Royal Family onto the Buckingham Palace balcony for a flypast. Those close to Charles have said he is “very much looking forward” to his official birthday parade.

The tradition, which dates back to the 17th century, involves 1,400 soldiers, 400 musicians and 200 horses. Usually the monarch rides down from Buckingham Palace to Horse Guards Parade via The Mall to inspect the troops. Charles rode on his horse Noble for his first Trooping as king last year, however, because of his health condition he has been advised to travel in a carriage this time.

King Charles, who recently attended D-Day commemorations in Portsmouth and Normandy, has been conserving his strength ahead of Saturday’s ceremony and pacing himself on the advice of his medical team.

Charles first attended Trooping the Colour when he was three years old and has been riding in the parade since 1975 and was said to have told his medical team that his attendance at tomorrow’s event was crucial.

According to former Buckingham Palace spokesman Dickie Arbiter: “It was one of the non-negotiables, you really cannot imagine Trooping the Colour without the monarch. I understand the king was determined to be at his birthday parade. Last year he was on horseback but this year his medics have said no, because of his condition. It’s all a question of balance.

The king was able to do Portsmouth and Normandy and left William to the international bit. That was enough for him, it was tiring and it’s a case of being safer than sorry. Riding a horse during the parade using only one hand can be dangerous, those horses can be frisky.”

Arbiter adds that even a spot of rain, predicted for Saturday, will not detract from what promises to be a special day although if there is low cloud cover the flypast could be scaled back.

“The big question is the weather and the forecast is 40-60 percent rain which could ruin the flypast, but the late Queen did Trooping come rain or shine and Charles is following in her footsteps. He is having treatment for cancer, but he is still doing this event.

It is part of the fabric of monarchy, and it’s also important to the people.

They like a good pageant and they will turn out and watch all the way from Horse Guards past St James’s Park and up the Mall. It’s part of our way of life.”

It is expected that all working members of the Royal Family including Princess Anne and the Duke and Duchess of Edinburgh will be present on the balcony along with Prince William. It is hoped that Prince George, Princess Charlotte and Prince Louis may also appear on the balcony but there is a question mark over whether Kate Middleton, who is also undergoing cancer treatment, will be able to attend.

The Princess of Wales was due to inspect her first Colonel’s Review of the Irish Guards at a rehearsal last week but was unable to attend. Kate wrote a letter to the Irish Guards, who are presenting their colours to the King this year, saying: “I hope I am able to represent you all very soon.”