On Saturday, King Charles will step onto the Buckingham Palace balcony for Trooping the Colour, the centuries-old annual military ceremony that celebrates the sovereign’s birthday.

It is expected that he will be joined by Queen Camilla, Prince William, Kate Middleton, Prince George, Princess Charlotte, and Princess Louis in what is seen as a show of support for the working royals. The Duke and Duchess of Edinburgh, Princess Anne and her husband Vice Admiral Sir Timothy Laurence, and the Duke and Duchess of Gloucester, who all carry out engagements on behalf of the King, are also expected to attend.

Trooping the Colour is one of the most important events in the royal calendar with the King and Queen at its center, flanked by the Wales family and supported by an ever-diminishing group of senior working royals. It is, according to Dickie Arbiter, former press secretary to the late Queen and King Charles, one of the occasions the King most looks forward to and his way of rewarding the family members who represent the crown.

“It’s an important date in the diary, and always a favorite occasion for the royals. These days, we see a much smaller line-up of royals on the Buckingham Palace balcony, but it is significant nonetheless, because it is the monarch’s way of thanking the family members who travel around the country and overseas representing the Crown,” he said.

There are not that many ways that King Charles can thank the working royals other than awarding them honors, so having them up there on the balcony is important. “The late Queen Elizabeth always enjoyed Trooping the Colour. Although it was a state event, the Queen used it as a chance to show the royals as a family to the world and that was a very powerful image,” said Arbiter.