The 75-year-old monarch, who has stepped back from major public engagements while receiving treatment, was applauded by members of the public as he left St George’s Chapel and urged to “keep going strong”.
The King went walkabout, chatting and shaking hands with well-wishers after attending the traditional Easter Sunday church service at Windsor Castle in a rare public appearance since he was diagnosed with cancer.
The 75-year-old monarch, who has stepped back from major public engagements while receiving treatment, looked in good spirits for the occasion where he was joined by the Queen and other members of the Royal Family.
As he emerged from St George’s Chapel, King Charles was greeted by cries of “Happy Easter” and applause from the public gathered outside, while Queen Camilla was presented with a posy of white and yellow flowers by a young boy.
One man told the head of state: “Keep going strong and never give in.”
Light-heartedly, he replied: “I have to obey my instructions.”
The Prince and Princess of Wales were not at the service, coming just over a week after Kate released an emotional video message revealing she had started preventative chemotherapy for cancer.
Earlier, as King Charles, wearing a dark coat and blue tie, arrived, one person shouted “Happy Easter”, to which he gestured with his arm and responded: “And to you.”
Anne Daley, 65, from Cardiff, Wales, holding up a Welsh flag, said: “He had a lovely smile. He looked well.
“I think he was happy that we’ve all come.”
The Princess Royal and her husband Vice Admiral Sir Timothy Laurence, the Duke and Duchess of Edinburgh, Prince Andrew, the Duke of York, and Sarah, Duchess of York, were among those to attend.
Royal biographer Robert Hardman hailed the service as a “considerable turning point” for the royal household.