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.

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. 

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."

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. 

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.