The 75-year-old king, who recently took part in a church service at Sandringham, his country estate, seemed upbeat according to reports. He humorously remarked on his appearance as being an illusion after Sunak commented on his well-being.

Sunak assured the king of the nation's solidarity, to which Charles responded by expressing how the outpouring of messages had deeply moved him.

He revealed his cancer diagnosis on February 5 and began treatment at Sandringham following the discovery of the illness, alongside treatment for a non-malignant enlarged prostate. His reign began 17 months prior, after the passing of Queen Elizabeth II at age 96.