London, UK - Queen Camilla, wife of Britain's King Charles III, said Thursday that her husband, who has been diagnosed with cancer, is "doing extremely well" under the circumstances.

King Charles has been "very touched by all the letters and the messages the public have been sending from everywhere," she said during a trip in southern England.

"Well, he's doing extremely well under the circumstances," Camilla said, adding that all the kind messages the king had received were "very cheering."

The Queen left King Charles at the royal country residence of Sandringham, in the East of England, where the couple moved on Tuesday.

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Less than 18 months after succeeding his mother, Queen Elizabeth II, to the throne upon her death, the 75-year-old sovereign began treatment on Monday for an unspecified form of cancer.

While he will continue to perform some administrative duties, the monarch will be absent from public life for an indefinite period.

On Tuesday, Prime Minister Rishi Sunak said the cancer had been "caught early."

Downing Street said on Wednesday that the king's weekly audience with the prime minister had taken place by phone, a rare detail for this traditional and totally private meeting between the sovereign and his head of government.

The meetings should resume in person within two weeks, according to the British media.