The King has been diagnosed with a form of cancer, Buckingham Palace has announced.
The Palace confirmed the disease, which is not prostate cancer, was discovered while the King was being treated in hospital for an enlarged prostate.
The Duke of Sussex is to fly to the UK in the coming days to see his father and has spoken to Charles about his diagnosis, a source close to Harry said.
Buckingham Palace said the King personally called both Harry and the Prince of Wales – as well as his siblings the Princess Royal, the Duke of York and the Duke of Edinburgh – to share news of his health.
Heir to the throne William is understood to be in regular contact with his father.
William appeared to be stepping up, with his return to official duties this week after the Princess of Wales’s abdominal surgery announced by Kensington Palace just hours before Buckingham Palace revealed Charles’s diagnosis.
US President Joe Biden expressed his concern for the King and said he planned to call Charles to wish him well.
He told reporters: “I’m concerned about him. Just heard about his diagnosis. I’ll be talking to him, God willing.”
Prime Minister Rishi Sunak was among those who wished the King a full and speedy recovery, while Labour leader Sir Keir Starmer also issued a get well message to the head of state.
Meanwhile, the King has already started a schedule of regular treatments and is said to be receiving expert medical care from a specialist team, but has been advised to postpone his public-facing duties.
The Palace declined to confirm the type of cancer.
Charles will carry on working behind the scenes on his red boxes – his state business and official papers, and returned from Sandringham to London on Monday to commence treatment as an out-patient.
He remains at home, most likely in Clarence House, his favoured residence in the capital.
Buckingham Palace said in a statement: “During The King’s recent hospital procedure for benign prostate enlargement, a separate issue of concern was noted.
“Subsequent diagnostic tests have identified a form of cancer.
“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.
“The King is grateful to his medical team for their swift intervention, which was made possible thanks to his recent hospital procedure.
“He remains wholly positive about his treatment and looks forward to returning to full public duty as soon as possible.
“His Majesty has chosen to share his diagnosis to prevent speculation and in the hope it may assist public understanding for all those around the world who are affected by cancer.”
It is understood there are no current plans to appoint Counsellors of State – members of the royal family who step in when a monarch cannot fulfil their duties.
The King has rearranged or postponed any forthcoming public engagements, but it is understood to be too early to say when Charles will return to full public duties, although he is said to be looking forward to doing so as soon as possible.
A Palace spokesman added: “His Majesty would like to apologise to all those who may be disappointed or inconvenienced as a consequence.”
The Palace has called for the King’s privacy to be respected, especially during his treatment, but said the monarch wanted to make his diagnosis public because of his long-running support for cancer charities.
The spokesman said: “No further details are being shared at this stage, except to confirm that His Majesty does not have prostate cancer.”
He added: “The King has elected to make his diagnosis public once the schedule of treatment had begun, noting that as Prince of Wales he was patron of a number of cancer-related charities.
“In this capacity, His Majesty has often spoken publicly in support of cancer patients, their loved ones and the wonderful health professionals who help care for them.”
Charles, 75, was discharged from the London Clinic a week ago after undergoing treatment on an enlarged prostate.
The shock news is the latest health scare to hit the royal family at the start of 2024, coming after the King’s hospital stay, Kate’s major abdominal surgery and Sarah, Duchess of York’s diagnosis of skin cancer.
Buckingham Palace announced on January 16 that the King was to have treatment for an enlarged prostate, but that the condition was benign.
The Palace announced the King’s cancer diagnosis at 6pm on Monday.
Charles, who acceded to the throne just 17 months ago, was last seen on Sunday when he attended church in Sandringham, but looked cheery as he walked along and waved at well-wishers.