Britain’s King Charles III has started a schedule of regular treatments after being diagnosed with cancer following his recent hospital procedure for benign prostate enlargement and will be postponing his public duties, Buckingham Palace has said.

While the palace has not specified the form of cancer, it said the 75-year-old monarch has started treatment and remains “wholly positive”.

He will be postponing his public duties on medical advice but will continue with his duties as a Head of State such as essential paperwork and private meetings.

“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,” reads the Buckingham Palace statement on Monday.

“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,” it said.

The statement noted that 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 added.

The Palace released a new unseen portrait of the King to accompany the announcement, showing him in a formal pose in a suit and tie with his hands behind his back during his state visit to France in September.

Over the weekend, King Charles was photographed waving after he and Queen Camilla attended a church service in Sandringham, Norfolk, marking his first public appearance since being discharged from the London Clinic last Monday.

He has since travelled from Sandringham to London to begin treatment as an outpatient and is now at his palace in London.

“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," British Prime Minister Rishi Sunak said on X.

Labour leader Sir Keir Starmer and Commons Speaker Lindsay Hoyle also wished him a speedy recovery.

US President Joe Biden expressed his concern and said he would speak to the King.

In a post on X, he later said: "Navigating a cancer diagnosis, treatment, and survivorship takes hope and absolute courage. Jill and I join the people of the United Kingdom in praying that His Majesty experiences a swift and full recovery." Biden's son, Beau, died of brain cancer aged 46.

The King is said to have informed both his sons, William and Harry, personally about his diagnosis and Prince William is in regular contact with his father.

Meanwhile, sources said that Prince Harry, who lives in the US, has spoken to his father and plans to travel to the UK to see him in the coming days.

Charles became King in September 2022 when his mother Queen Elizabeth II died at the age of 96.

News of the king's diagnosis comes as his daughter-in-law Kate, Princess of Wales, recovers from abdominal surgery that saw her hospitalised for about two weeks.

The King chose to go public about his cancer treatment as he had been a patron of several cancer-related charities when he was Prince of Wales, a spokesman said.

"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." He had also gone public about his prostate treatment, to encourage more men to get prostate checks.

The Royal Society of Medicine thanked the King for highlighting "how cancer is indiscriminate" and urged members of the public eligible for cancer screenings to make an appointment.

"Please don't be shy - the more information we have the better to help - hopefully - rule out cancer or, if not, put you on the most suitable treatment pathway," its president, Dr Jay Verma, said.

There are more than 200 types of cancer - the most common ones in the UK are breast, lung, prostate and bowel, according to the National Health Service website. For many types of cancer, the chance of getting it increases with age. The King and Queen are scheduled to visit Canada in May, and Australia, New Zealand and Samoa for the Commonwealth Heads of Government Meeting in October.

The Palace has yet to confirm whether the tours will go ahead, with no date suggested for the King's return to full public duties.