King Charles III attended church Sunday for the first time since his cancer diagnosis.

Walking beside Queen Camilla, Charles arrived at St. Mary Magdalene Church, close to Sandringham House in eastern England where he retreated to recuperate following his first treatment for an unspecified form of cancer.

The appearance came a day after he expressed thanks for the messages of support he has received from the public. In a statement issued late Saturday, the monarch said that such 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 organizations which support cancer patients and their families across the U.K. and wider world," he said in a statement.

"My lifelong admiration for their tireless care and dedication is all the greater as a result of my own personal experience."

Buckingham Palace announced the diagnosis on Monday. Charles was last seen on Tuesday as he left his home at Clarence House in London after starting his treatment.

The palace has not shared many details on Charles' diagnosis, except to say that it was not prostate cancer. Details about the health of members of the royal family have traditionally not been disclosed to the public, making it notable that the palace decided to release any information at all.

The king's diagnosis comes amid a time of troubling health news within the family, less than two years after Queen Elizabeth's death in September 2022. Charles' daughter-in-law, Catherine, last month underwent abdominal surgery for an unspecific ailment. Kensington Palace said in a statement on Jan. 29 that she was recovering at home, nearly two weeks after the initial statement that she had undergone the medical procedure at a London hospital. Per the initial statement from the palace, she is likely to be recuperating for several months.

Her husband, Prince William, who is next in line for the throne, spoke publicly last week for the first time since the dual diagnoses, noting at a charity gala that the "past few weeks have had a rather medical focus."

"I'd like to take this opportunity to say thank you for the kind messages of support for Catherine and for my father, especially in recent days," William said on Feb. 8.

William's brother, Prince Harry, who has been estranged from the family, flew to Britain last week to visit his father. 

Additionally, Sarah Ferguson, the ex-wife of Charles' brother Prince Andrew, announced in January that she had been diagnosed with skin cancer just months after she battled breast cancer.  

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• King Charles III
• British Royal Family
• Prince William Duke of Cambridge
• Prince Harry Duke of Sussex
• Catherine Princess of Wales