King Charles has been diagnosed with cancer and is already receiving treatment that will prevent him from undertaking public duties for the immediate future, Buckingham Palace has announced. Although no further details about what type of cancer he has are being released at this stage, Buckingham Palace said it was not prostate cancer. It was discovered when the 75-year-old monarch recently underwent treatment at the London Clinic for a benign enlarged prostate. Buckingham Palace said the king “remains wholly positive about his treatment”. He began regular outpatient treatments on Monday, and although he has been forced to postpone public-facing engagements, he will continue with his constitutional role as head of state, including paperwork, his red boxes and private meetings. The king personally informed both his sons, the Prince of Wales and Duke of Sussex, of his diagnosis, as well as his three siblings, the Princess Royal, Duke of Edinburgh and Duke of Sussex. Prince Harry had spoken with his father about his cancer diagnosis and would be travelling to the UK to see him in the coming days, a source close to Harry said. It is believed he will travel alone with the Duchess of Sussex staying in the US with the couple’s two children – Prince Archie and Princess Lilibet. In a statement, Buckingham Palace said: “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.” The king returned to London from Sandringham on Monday morning to begin treatment as an outpatient. It is understood there are no plans to appoint counsellors of state, who can be appointed to stand in if the monarch is incapacitated. At present, these include Queen Camilla, Prince William, Princess Anne and Prince Edward, with Prince Harry and Prince Andrew no longer to be called on as non-working royals. It is expected that Charles will continue to be available for Privy Council meetings, but details of how they will take place are still being worked through. It is also expected that alternative arrangements will be made for his weekly audience with the prime minister should doctors advise him to minimise any in-person contact. He was last seen in public at Sandringham in Norfolk on Sunday, where he attended a church service with the queen, which was the first time he had been seen since he was discharged from the London Clinic. He smiled and waved to wellwishers as he walked to St Mary Magdalene church in the village. Charles apologised for the medical decision to postpone his forthcoming public duties after his cancer diagnosis. A palace spokesperson said: “Regrettably, a number of the king’s forthcoming public engagements will have to be rearranged or postponed. His Majesty would like to apologise to all those who may be disappointed or inconvenienced as a consequence.” It is understood details of the king’s diary are still being worked on and it is not yet known when a full programme of engagements will begin. The palace said the queen would continue with a full programme of public duties. The postponement of his public-facing engagements comes as Catherine, Princess of Wales, recovers at home after planned abdominal surgery, also at the London Clinic. She has determined to keep her medical details private, although her condition was said to be non-cancerous. But with her also out of action – she is not expected to return to public duties until after Easter – it presents problems for the monarchy, which is significantly diminished in the number of working royals because of the departure of the Duke and Duchess of Sussex. Kensington Palace announced earlier on Monday that the Prince of Wales, who took time off while his wife was in hospital, would resume public duties this week by conducting an investiture on Wednesday at Windsor Castle, followed by a gala fundraising event for the London air ambulance in the evening. The announcement brought a stream of messages from wellwishers. The prime minister, Rishi Sunak, reacted to the news by tweeting: “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.” The Labour leader, Keir Starmer, wished the king “all the very best for his recovery”. He tweeted: “On behalf of the Labour party, I wish his majesty all the very best for his recovery. We look forward to seeing him back to swift full health.” Joe Biden said he was “concerned” about the king and planned to call him later. He told reporters: “I’m concerned about him. Just heard about his diagnosis. I’ll be talking to him, God willing.” The US president, whose son Beau died of brain cancer in 2015, later tweeted: “Navigating a cancer diagnosis, treatment, and survivorship takes hope and absolute courage. [My wife] Jill and I join the people of the United Kingdom in praying that His Majesty experiences a swift and full recovery.” Former US president Donald Trump wrote on social media : “He is a wonderful man, who I got to know well during my presidency, and we all pray that he has a fast and full recovery!” The Commons speaker, Sir Lindsay Hoyle, told MPs: “I know the whole house will wish to join me in expressing our sympathies with his majesty the king following the news announcement this evening. “Our thoughts are, of course, with his majesty and his family, and we’d all wish to send him our very best wishes for the successful treatment and a speedy recovery following tonight’s news.” Liberal Democrat leader, Sir Ed Davey, posted on X: “The Liberal Democrats join the rest of the nation in wishing a full and quick recovery to His Majesty.” Former prime ministers Boris Johnson and Liz Truss also sent their best wishes. Johnson posted on X: “The whole country will be rooting for the King today. Best wishes to Charles III for a full and speedy recovery.” Truss posted: “Sending every best wish to His Majesty The King and the Royal Family as he undergoes his treatment for cancer. He will be in our thoughts and prayers. God Save The King!” Scottish first minister, Humza Yousaf, said: “My thoughts and prayers are with His Majesty the king and I hope for a speedy recovery and return to public life. My thoughts are also with Her Majesty the queen and other members of the royal family at what I know will be a worrying time.” Mark Drakeford , the first minister of Wales, wished him a “full and swift recovery”. In a post on X, he said: “I’m saddened to hear the news that HM King Charles III is facing further health challenges. My thoughts and those of people across Wales will be with him and his family this evening. I send my very best wishes as he starts treatment for a full and swift recovery. Gwellhad buan.” Northern Ireland’s first minister, Michelle O’Neill, wished him a speedy recovery. “I am very sorry to hear of King Charles’ illness and I want to wish him well for his treatment, and a full and speedy recovery,” she posted on X. DUP leader Sir Jeffrey Donaldson posted: “Sending His Majesty the King every good wish as he commences his treatment. We pray for a full and speedy recovery.” The king has largely enjoyed good health throughout his life. The first signs of any significant concern came with Buckingham Palace’s surprise announcement on 17 January that he had sought treatment for an enlarged prostate. The palace stressed that his condition was benign and that he would attend hospital the following week for a corrective procedure. Charles had checked in to the London Clinic on Friday 26 January, and was discharged three days later on Monday 29 January, the same day that Kate was also discharged. The queen told wellwishers at an engagement at a Maggie’s cancer support centre at the Royal Free hospital in London on Wednesday that Charles was “getting on, doing his best.” He was said to be personally keen to share details of his benign prostate diagnosis to encourage other men who may be experiencing symptoms to get themselves checked.