King Charles III has been diagnosed with a form of cancer and has begun treatment, Buckingham Palace said on Monday, just a week after he was discharged from hospital for prostate surgery.
The announcement prompted a flood of messages of support, with the 75-year-old monarch's estranged son Prince Harry saying he had spoken with the king about his diagnosis and would visit his father.
His younger son who now lives in California with his wife Meghan said he would travel to see the king in the UK over the coming days, a source close to Harry said.
Charles, who became king upon the death of his mother, Queen Elizabeth II, on September 8, 2022, has generally enjoyed good health, barring injuries from polo and skiing.
But the palace said that during his recent hospital procedure for benign prostate enlargement "a separate issue of concern was noted".
"Subsequent diagnostic tests have identified a form of cancer," the palace said in a statement, adding that he had begun treatment, but without elaborating on the type of cancer found or how advanced it was.
The palace said the king "remains wholly positive" and "looks forward to returning to full public duty as soon as possible".
In the meantime he had been advised by doctors to postpone public duties although he would continue to "undertake state business and official paperwork as usual", it said.
The king won plaudits for being open about his benign prostate condition, with doctors saying many more members of the public had come forward with symptoms.
The palace added that Charles had chosen to share his cancer diagnosis "to prevent speculation and in the hope it may assist public understanding for all those around the world who are affected by cancer".
Messages wishing Charles a swift recovery flooded in following the shock statement from the palace.
"Wishing His Majesty a full and speedy recovery. I have no doubt he'll be back to full strength in no time and I know the whole country will be wishing him well," wrote Prime Minister Rishi Sunak on X, formerly Twitter.
US President Joe Biden said he was "concerned" about King Charles while Canadian Prime Minister Justin Trudeau said he and the nation were "thinking of his majesty King Charles III as he undergoes treatment for cancer".
"We're sending him our very best wishes - and hoping for a fast and full recovery," he added.
The diagnosis will prolong a frontline shortage of royals created by Charles's prostate procedure and the almost simultaneous hospitalisation of Catherine, Princess of Wales.
Catherine, 42, who is the wife of Charles's son and heir to the throne Prince William, underwent abdominal surgery at the same hospital where Charles was treated.
She left last Monday on the same day as Charles following a stay of around of two weeks and may not return to public duties until late March.
Her husband William, 41, also stepped back temporarily from planned engagements to help care for their three children.
The pair's absence left Queen Camilla, Charles's 76-year-old wife, as the most visible face of the royal family.
William is expected to return to royal duties this week.
At the time of Catherine's operation, Kensington Palace stressed that her condition was not linked to cancer, without elaborating.
King Charles III looks on during an official welcoming ceremony at the Arc de Triomphe in Paris on September 20, 2023, on the first day of a state visit to France. AFP