King Charles made the comments during the first formal face-to-face meeting with UK Prime Minister Rishi Sunak at Buckingham Palace on February 21.

"I've had so many wonderful messages and cards," he said.

"It's reduced me to tears most of the time," he said.

Prime Minister Sunak began the meeting by telling King Charles it was wonderful to see him looking so well.

"Well, it's all done by mirrors," the monarch quipped.

Prime Minister Sunak assured the King everyone was "behind him" and highlighted the cancer awareness his diagnosis has raised.

King Charles said he had heard about the increased support for cancer services in the UK, "many of which I've been patron for years".

The King has started a schedule of regular treatments but had been advised to postpone his public-facing duties.

He has said he intends to continue to perform his state duties.

King Charles, 75, spent three nights in hospital last month after undergoing a corrective procedure for an enlarged prostate when a separate issue of concern was noted.

The palace said that tests had identified a form of cancer.

The palace did not give any details about King Charles' cancer but a royal source said that it was not prostate.