The first of these will be Tuesday's visit to a cancer treatment centre to meet patients and medical specialists. The Palace has also announced Charles and his wife Queen Camilla will host a state visit by the Japanese Emperor Naruhito and his wife Empress Masako in late June.

Charles' health issues began in January when it was revealed that he would be admitted to hospital to have a corrective procedure for a benign enlarged prostate. The following month, the palace said tests had uncovered the presence of a "form of cancer", but gave no further details beyond saying it did not involve his prostate.

He has rested and undergone treatment for the disease since then, continuing with official state duties in private. He was well enough to greet well-wishers after an Easter church service at the end of March. Although his diary will be carefully managed to minimise any risks to his health, the palace said he might attend some annual events such as 'Trooping the Colour' military parade in June, as well as commemorations to mark the 80th anniversary of the World War Two D-Day landings, also in June.

Charles' illness came less than 18 months after he succeeded his mother Queen Elizabeth. His nephew Peter Phillips has said the monarch, who is renowned for hard work, had found the limitation imposed by his treatment frustrating. Also absent has been Charles' daughter-in-law Kate, wife of his son and heir Prince William, who is undergoing preventative chemotherapy after tests in the wake of major abdominal surgery revealed cancer had been present.