London society is uneasy about King Charles’ health after he missed a major event that he had long been expected to attend, Page Six hears.

The ailing monarch, 77, has attended several affairs this year, including the Zoological Society of London’s 200th anniversary on July 9, plus official trips to Washington, DC, and Bermuda in early May.

But last weekend he was noticeably absent from the glittering festivities surrounding the 100th anniversary of the Royal Ballet School, of which he is the official patron, we’re told.

We’re told the absence jangled nerves, leading royal insiders to whisper that the king’s official calendar is quietly being cut back.

The head royal’s public appearances are routinely planned years in advance, but we’re told that some he committed to months ago are now being rearranged to allow Queen Camila, Prince William, Princess Kate and other members of the royal family to step in.

The Crown was represented at the ballet bash by Princess Margaret’s daughter, Lady Sarah Chatto, who is also the president of both the Royal Ballet School and the Birmingham Royal Ballet.

The celebrations included back-to-back receptions and performances, one at the Royal Opera House on Thursday, Oct. 8, followed by a black-tie gala dinner at the White Hall Palace on Friday, Oct. 9.

Attendees included former Prime Minister Sir John Major and various ballet and art world luminaries.

Buckingham Palace announced on Feb. 5, 2024, that Charles, now 77, had been diagnosed with “a form of cancer” after undergoing a procedure to treat an enlarged prostate.

He is still undergoing treatment for the as-yet-unidentified form of the disease.