Britain's King Charles III greets a guest during a reception at Buckingham Palace, London, for guests from a wide range of media organisations across the country, Wednesday March 26, 2025. (Aaron Chown, Pool via AP)2025-03-27T21:10:20Z LONDON (AP) King Charles III was briefly hospitalized for observation on Thursday after experiencing temporary side effects related to a scheduled cancer treatment, Buckingham Palace said in a statement. His engagements for Thursday afternoon and Friday were canceled.His majesty has now returned to Clarence House and as a precautionary measure, acting on medical advice, tomorrows diary program will also be rescheduled, the palace said. His majesty would like to send his apologies to all those who may be inconvenienced or disappointed as a result.The kings health has been closely watched ever since early last year when he announced that he had been diagnosed with an undisclosed form of cancer. Charles, 76, stepped away from public duties for about three months but continued fulfilling state duties, such as reviewing government papers and meeting with the prime minister. Charles cancer diagnosis has heaped pressure on the British monarchy, which is still evolving after the 70-year reign of the late Queen Elizabeth II.When he succeeded his mother in September 2022, Charles task was to demonstrate that the 1,000-year-old institution remains relevant in a modern nation whose citizens come from all corners of the globe. But this task takes much time and energy. Although the duties of a constitutional monarch are largely ceremonial, the royal whirl can be exhausting. Besides the occasional procession in full royal regalia, there are meetings with political leaders, dedication ceremonies and events honoring the accomplishments of British citizens. That added up to 161 days of royal engagements during Charless first year on the throne.Charles illness came as his daughter-in-law, Kate, the Princess of Wales, was also diagnosed with cancer. Kate, the wife of Prince William, took more than six months off before returning to public duties in late September.