London — Queen Camilla said Thursday evening that King Charles III was "doing extremely well under the circumstances," several days after Buckingham Palace revealed that the monarch had been diagnosed with an unspecified form of cancer and was undergoing treatment.

Speaking at a concert celebrating the work of local charities in England's Salisbury Cathedral, Camilla said Charles was "very touched by all of the letters and messages the public have been sending from everywhere," and that he found them "very cheering."

Charles was diagnosed with cancer while he was undergoing treatment for an enlarged prostate last month. Buckingham Palace said he would step back from his public duties during his treatments, but it has not said how long they will take.

Will Camilla fill in for Charles?

Charles will continue to carry out his behind-the-scenes state duties, such as reviewing and signing official papers. It is only his public appearances that he'll be scaling back on while he undergoes cancer treatment.

Though Camilla has the title of queen, she is a "Queen Consort" not a "Queen Regnant" like Charles' late mother Queen Elizabeth II. That means Camilla is not in the royal line of succession and cannot fill in for Charles, the U.K.'s official head of state, in his public engagements as such.

"It's rather like if [President] Biden was ill, Jill wouldn't be giving out the Congressional Medal of Honor," former BBC royal correspondent and historian Wesley Kerr told CBS News. "Camilla, although she's the queen, she's not going to do any of the head of state stuff. Filling in for the head of state stuff… that would be William. William is, as it were, the vice president."

Will Camilla's schedule change during Charles' treatment?

Camilla's schedule of events is not announced ahead of time for security reasons, so the public won't know if she has changed any of her plans due to her husband's cancer diagnosis.

"She doesn't have the heaviest program, so a lot of her engagements would have been with him. If there is a reception at Buckingham Palace or something, she's helping to host the reception. So many of those will fall from the diary" due to the king's absence from his public duties, Kerr told CBS News.

But he said many of Camilla's engagements, about one per day, have to do with charities or causes that she supports personally, and she will most likely keep those booked.

"I'd have thought she'll end up probably doing about the same number of engagements this year as last year," Kerr said, adding that if there is a particularly grueling period of cancer treatment for Charles, "they would probably keep her schedule free so, at the very least, in the evening she was available to see him."

What happens to Camilla when Charles dies?

When King Charles dies, Prince William immediately becomes the king, and his wife Kate, who's had her own recent health issues, becomes the queen. Camilla, if she outlives her husband, would still be known as Queen Camilla, "but in effect she would be the Dowager Queen," Kerr told CBS News.

Charles and Camilla do not currently live at Buckingham Palace, which is undergoing extensive renovations, but at nearby royal residence in London called Clarence House. Kerr said it was likely that Camilla would maintain at least temporary residence there in the event of her husband's death. 

The queen, Kerr notes, "has her own house in Gloucestershire anyway, a country house called Ray Mill, which is her personal property, which she owned before she married Charles because she's independently quite well-off, and I suspect that she would have a London residence at Clarence House and she would have a limited program of engagements." 

What do Brits think of Camilla?

"Anybody that meets Camilla likes her, to be honest," Kerr told CBS News. "She's not at all grand, and everybody can see that [Charles] has changed since they got married — that he is much more relaxed when they're doing engagements together."

Kerr said Charles and Camilla are "a great love match, really," and he believes the British public have seen that.

"She visited him in the hospital — he was in for three days, and she visited like four times," Kerr said. "That's a lot, really, even for some normal people."

Kerr said that while Camilla may have been unpopular in the past, given her very public part in the collapse of Charles' first marriage to Princess Diana, that seems to have changed.

"People think, 'Well, that's rather sweet. Whatever went wrong in the past, they're obviously very happy together.'"

In:
• King Charles III
• British Royal Family
• Prince William Duke of Cambridge
• Queen Camilla

Haley Ott

Haley Ott is cbsnews.com's foreign reporter, based in the CBS News London bureau. Haley joined the cbsnews.com team in 2018, prior to which she worked for outlets including Al Jazeera, Monocle, and Vice News.

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