The King has spoken of the “shock” of discovering he had cancer as the British monarch returned to public duties for the first time since his diagnosis in February.

A smiling and healthy-looking King, 75, met patients at a cancer centre in London on Tuesday (UK time) and was able to relate to some of their experiences.

While sitting and chatting with Lesley Woodbridge, 63, the King expressed an understanding of what it was like receiving the dreaded news from doctors.

“It’s always a bit of a shock isn’t it, when they tell you,” he agreed.

Relating to Woodbridge’s experience he added: “I’ve got to have my treatment this afternoon as well.”

One person asked the King how he was faring, to which he replied: “I’m all right, thanks. Not too bad.”

The King holds the hand of patient Asha Millan at the cancer centre. Photo: Getty

Buckingham Palace announced on Friday that doctors were sufficiently pleased with the King’s response to treatment and he would be able to resume some public-facing engagements.

The first of these was a joint visit with the Queen to the University College Hospital Macmillan Cancer Centre, where both met patients and medical specialists.

The King was greeted by cheers from staff and patients when he arrived and then began listening to people’s stories.

The monarch, who has also become patron of the charity Cancer Research UK, looked cheerful, waving to those gathered outside on his arrival on Tuesday.

The King’s 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, Buckingham 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 has said the King 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 II D-Day landings, also in June.

The palace has confirmed the King and Queen will host a state visit by the Japanese Emperor Naruhito and his wife Empress Masako in late June.

The King’s illness came less than 18 months after he succeeded his mother Queen Elizabeth. His nephew Peter Phillips has said the monarch, who is known for his desire to keep busy, had found the limitation imposed by his treatment frustrating.

Also absent has been the King’s daughter-in-law Kate, wife of his son and heir Prince William. She is having preventative chemotherapy after tests following major abdominal surgery revealed cancer had been present.

-with AAP