The King has been seen in public for the first time since his cancer diagnosis was revealed, as royal watchers speculate about how a slimmed-down royal household will function.

The King and Queen were photographed smiling and waving as they left their Clarence House home and drove to Buckingham Palace on Tuesday afternoon (local time).

The King’s helicopter took off from Buckingham Palace shortly after, and was later seen landing at the royals’ Sandringham estate in Norfolk.

Earlier, Prince Harry was spotted arriving separately at Clarence House after landing in London from the US to be with his father.

Multiple media outlets are reporting the reunion between the estranged monarch and his younger son appeared to last about 45 minutes before the King and Queen were photographed departing.

A royal source said there were no plans for Harry to see his elder brother, heir-to-the-throne Prince William, during his visit to Britain.

The King puts on a brave face as he and the Queen leave Clarence House. Photo: Getty

Royal reshuffle

On Monday (local time), the 75-year-old King returned from Sandringham to London to commence treatment as an outpatient.

We know he will not be “public facing” and is “deeply frustrated” he can’t go out and meet people.

The news sent shockwaves around the world when Buckingham Palace abandoned royal protocol by announcing his cancer diagnosis on Tuesday (AEDT), discovered during the King’s recent treatment for an enlarged prostate.

According to ITV‘s royal editor, Chris Ship, the King won’t be replaced, but it is a “major setback”.

Temporarily installing counsellors of state or even appointing Prince William as regent are being talked about on the airwaves, but the monarchy has not reached that point.

“We are told there will be no need to install counsellors of state, who are other senior members of the royal family who can stand in for a monarch when he or she is incapacitated,” Ship said.

Counsellors of state include the sovereign’s spouse and the next four people in the line of succession who are over the age of 21.

The official royal website lists counsellors of state as the Queen, Prince William, Prince Harry, Prince Andrew and Princess Beatrice; however, the latter three have been bumped to make way for Princess Anne and Prince Edward.

“The King will still attend to his red boxes – the official papers sent to him by the government,” Ship said.

He will also carry on working behind the scenes on state business and will continue his regular meeting with British PM Rishi Sunak.

Ship said this “will put a greater burden on Queen Camilla, who will more than ever be living up to her title as Queen Consort in supporting the King”.

“It also puts a greater workload on … Prince William.”

The Queen and Prince William were jointly appointed counsellors of state at the State Opening of Parliament in 2022. Photo: AAP

Worst-case scenario

The King was expected to tour Australia in late 2024, as part of a broader trip to the region for the Commonwealth Heads of Government meeting in October in Samoa.

It is not yet known which international commitments will be fulfilled by the King and Queen this year.

With the counsellors of state being considered a “temporary” measure, if the “incapacity of the King becomes more permanent, then the Regency Act of 1937 “provides for a regent”.

“By reason of infirmity of mind or body incapable of performing royal functions … and certified by three out of five people (including Camilla),” constitution expert Professor Robert Hazell told the UK’s Radio Times.

“In that event, a regency is triggered and Prince William would become regent,” he says.

William has returned to official duties this week after wife Kate spent two weeks in hospital for planned abdominal surgery. She will be out of sight, recovering, until at least Easter.

Hazell believes the royal family has always put “duty above their own personal circumstances”. However, many, including Ship, say “there is certainly no prospect of a regency, the like of which we haven’t had for more than 200 years”.

The King’s former communications secretary Julian Payne told the BBC the palace will have prepared for a situation like this.

“Whilst this is an unwelcome surprise, I don’t think that it will require a significant new change to some of these structures that are in place.”