The palace statement said Charles was “grateful to his medical team for their swift intervention,” and insisted the king “looks forward to returning to full public duty as soon as possible.”

A source close to Charles’ younger son Harry, who lives in California, told the BBC the prince had spoken to his father and will be flying back to the U.K. to be at his side. The pair have met just once since Charles became king — at his coronation in May 2023.

Charles’ health had already been of some concern after he spent three days in a London hospital for prostate treatment last month.

Buckingham Palace revealed Monday night that during this treatment, “a separate issue of concern was noted.”

“Subsequent diagnostic tests have identified a form of cancer,” the statement said. “His majesty has today commenced a schedule of regular treatments, during which time he has been advised by doctors to postpone public-facing duties.

“Throughout this period, his majesty will continue to undertake state business and official paperwork as usual.”