Britain’s King Charles III has been diagnosed with cancer and will step back from public-facing duties while he undergoes treatment, Buckingham Palace announced Monday.

The update came after Charles, 75, attended a London hospital for a corrective procedure for an enlarged prostate last month.

Tests were carried out and revealed a “form of cancer,” the palace said in a statement on Monday. A royal source told CNN that the form of cancer detected was not prostate cancer, but did not specify further.

“His Majesty has today commenced a schedule of regular treatments, during which time he has been advised by doctors to postpone public-facing duties,” the palace said.

“Throughout this period, His Majesty will continue to undertake State business

and official paperwork as usual,” it added.

The King spent three nights at the London Clinic, a private hospital near Regent’s Park, for his recent procedure and was previously said to be “doing well” following the stint.

He was seen for the first time since his treatment on Sunday, appearing in good spirits as he waved to the public on his way to a Sunday morning church service in Sandringham, Norfolk. His wife, Queen Camilla accompanied him.

The royal source added that the King returned from Sandringham on Monday morning to begin outpatient treatment in London.

“The King is grateful to his medical team for their swift intervention, which was made possible thanks to his recent hospital procedure,” Buckingham Palace’s statement said. “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 palace concluded.