King Charles thanked the "selfless doctors and nurses" who supported him and his daughter-in-law Kate Middleton after they were both diagnosed with cancer.
On Wednesday, the 76-year-old gave his annual Christmas speech, which was filmed at Fitzrovia Chapel, the former chapel of Middlesex Hospital in London.
The broadcast came several hours after the monarch attended Christmas Day services at a church in Sandringham. Charles was accompanied by his wife Queen Camilla, his son Prince William, Kate and his three grandchildren.