The King has attended church with the Queen in his first public outing since the announcement of his cancer diagnosis.
Walking alongside Camilla and holding an umbrella, Charles arrived at St Mary Magdalene Church in Sandringham, Norfolk, on Sunday morning.
The King was seen wearing a brown coat and waving to the public before being greeted by the Rev Canon Dr Paul Williams at about 10.50am.
Charles is staying at Sandringham following his first bout of cancer treatment.
Buckingham Palace announced on Monday that the King, who acceded to the throne 17 months ago, has an unspecified form of the disease.
He was diagnosed after a “separate issue of concern was noted” and was investigated while he was being treated for a benign and unrelated prostate condition.
The 75-year-old King was seen in public for the first time since his cancer diagnosis as he left Clarence House in a car on Tuesday, the day after starting his treatment, following a brief reunion with the Duke of Sussex.
Charles has postponed all public-facing duties, but is continuing with behind-the-scenes work on his red boxes of state papers.
On Saturday the King thanked people for their “many messages of support and good wishes” and said it was “equally heartening” to hear how sharing his diagnosis has helped to promote public understanding of cancer.
In a message to the public, Charles said: “I would like to express my most heartfelt thanks for the many messages of support and good wishes I have received in recent days.
“As all those who have been affected by cancer will know, such kind thoughts are the greatest comfort and encouragement.
“It is equally heartening to hear how sharing my own diagnosis has helped promote public understanding and shine a light on the work of all those organisations which support cancer patients and their families across the UK and wider world.
“My lifelong admiration for their tireless care and dedication is all the greater as a result of my own personal experience.”
The message was signed “Charles R”.
The Palace has called for the King’s privacy to be respected, especially during his treatment, but said he wanted to make his diagnosis public because of his long-running support for cancer charities.
A host of medical professionals from different groups have commended the King’s candour over his health.
Chiara De Biase, director of support and influencing at Prostate Cancer UK, highlighted a 500% increase in people coming to the charity’s website for information and support in the week following the King’s announcement of his enlarged prostate condition in January.
The Prince of Wales may step in to represent his father at events, but no engagements are scheduled at the moment and the royal palaces will make arrangements if the need arises.
The King’s illness coincided with a hospital stay by the Princess of Wales, who underwent planned abdominal surgery.