What happens when a monarch falls ill? The plan for royal health issues explained

When King Charles's cancer diagnosis was made public on Monday, Buckingham Palace also laid out in broad strokes how the monarch's royal business is expected to unfold while he undergoes treatment.

Charles, 75,is "wholly positive" about his treatment for the undisclosed form of cancer, the palace said. But he is forgoing public duties while undergoing treatment.

• What questions do you have about King Charles's health? Send them to ask@cbc.ca.

He is expected, however, to continue with the formal constitutional affairs of state, the paperwork and private meetings such as his regular weekly session with British Prime Minister Rishi Sunak.

"Clearly his medical team is advising against public-facing engagements and so by making this announcement, it avoids speculation as to why the King will not be seen in public during this course of treatment," Toronto-based royal author and historian Carolyn Harris said in an interview.

"This is a way of managing public expectations."

While there are formal provisions for how official duties can be handled if the monarch cannot carry them out on a temporary basis because of illness or being overseas through the appointment of counsellors of state there is no indication they will be adopted at this time.

Charles's cancer diagnosis comes as his daughter-in-law, Catherine, Princess of Wales, continues to recover at home after abdominal surgery last month. She isn't expected to resume public duties until after Easter.

WATCH | Buckingham Palace announces King Charles III's cancer diagnosis:

King Charles diagnosed with cancer

8 months ago

Duration 7:03

King Charles III has been diagnosed with cancer and has begun treatment, Buckingham Palace says. The palace says the cancer is not related to the King's recent treatment for a benign prostate condition, but did not reveal what form of cancer he has.

As the two are out of the public eye, other senior members are expected to have a higher profile.

"It's clear the public face of the monarchy at this time is very dependent on three very hard-working royal women, Queen Camilla, Princess Anne and Sophie, the Duchess of Edinburgh," said Harris.

'"Although the direct line of succession is King Charles III, his son Prince William, the Prince of Wales, and then Prince George, it's going to be the senior royal women who are the most visible in the coming weeks."

What about Prince William?

The Prince of Wales, who is heir to the throne, will, however, have some public profile this week. He is returning to work after nearly a month away from public duties following Catherine's surgery.

WATCH |Londoners hope King Charles has afull recovery:

Londoners hope for King Charles's full recovery

8 months ago

Duration 1:00

Reacting to the news of King Charles's cancer diagnosis, people on the streets of London offered sentiments of sympathy and support for his health.

William, 41, will reward members of the public with special honours on the monarch's behalf at an investiture in Windsor on Wednesday.

Later that same day, William is expected to attend an annual fundraising gala for the London Air Ambulance in central London. William became patron of the organization after working as an air ambulance pilot for a little more than two years.

The back-to-back events will be William's first public appearances since Kensington Palace announced the Princess of Wales had undergone scheduled abdominal surgery last month. Catherine, 42, returned home to Windsor last Monday after recovering at the London Clinic for 12 days.

William took time away from his duties to support his wife and care for their three children: Prince George, 10, Princess Charlotte, 8, and Prince Louis, 5.

Catherine has not yet returned to public engagements. Kensington Palace did not disclose details of her procedure, but a statement said the operation was "successful" and that she was making "good progress" in her recovery.

Who are the counsellors of state?

The counsellors of state who could stand in for Charles officially are set out in law as his spouse Queen Camilla and the next four people in the line of succession who are older than 21 (except the heir, who has to be 18).

Counsellors of state can, according to the Royal Family's website, carry out duties such as attending Privy Council meetings, signing routine documents and receiving the credentials of new ambassadors to the United Kingdom.

As it stands now, the next four people in the line of succession older than 21 are Prince William, Prince Harry, Prince Andrew and Princess Beatrice.

But Harry stepped back from official duties and is living in California. Andrew also stepped back from public duties in the fallout after his disastrous television interview over his friendship with convicted sex offender Jeffrey Epstein.

Last fall, at the request of Charles, the pool of counsellors of state was expanded to include his sister, Princess Anne, and his brother, Prince Edward, both of whom held the role years ago, before they were bumped down in the line of succession.

"It no longer goes strictly down the line of succession as it did in the past because of the various scandals associated with Prince Harry and Prince Andrew and Prince Harry not [currently living]in the United Kingdom," said Harris.

In practice, it becomes a decision of the monarch whether counsellors of state are appointed.

"It's relatively loose. All the legislation says is just that the King has decided, or the monarch has decided to delegate their functions," said Craig Prescott, a constitutional expert and lecturer in law at Royal Holloway, University of London, in an interview.

"There's no sort of threshold of illness or anything. So it is in practice, I think it's the King's decision for counsellors of state It can all be very flexible."

WATCH | Prince Harry returns to England:

Prince Harry arrives in U.K. following King's cancer diagnosis

8 months ago

Duration 5:12

Prince Harry, who stepped down from royal duties almost four years ago, has arrived in Britain as messages of support for King Charles poured in from world leaders.

Have counsellors of state been appointed in the past?

Counsellors of state were routinely appointed when Charles's mother, Queen Elizabeth, was out of the country on overseas visits.

"Sometimes they acted, sometimes they didn't. It sort of just depended what happened, what needed their attention," Prescott said.

Counsellors of state were also appointed last year when Charles visited Romania on holiday but not when he was in Kenya on an official visit.

They were also appointed for the state opening of the British Parliament in the spring of 2022, when mobility and health concerns were limiting the public duties carried out by Elizabeth.

They were not, however, appointed earlier in Elizabeth's reign when she faced various health concerns, such as knee surgery in 2003.

There were times more recently when it might have been possible to consider counsellors of state, given the Queen's health, but that option was not pursued.

"She received Prime Minister Liz Truss just two days before her passing," said Harris.

"She was undertaking her duties as head of state right to the very end. In the case of King Charles III, it's clear that he's optimistic this is a treatable cancer. If that was to change and it became impossible for him to undertake any of the duties of head of state, this is where in the short term the counsellors of state would be very significant."