By Lauren Turner, BBC News
King Charles has given his "heartfelt thanks" for messages of support from the public, in his first statement since being diagnosed with cancer.
The 75-year-old monarch said: "As all those who have been affected by cancer will know, such kind thoughts are the greatest comfort and encouragement."
News of the diagnosis was announced by Buckingham Palace on Monday.
The King is being treated for an unspecified form of cancer and is currently staying at Sandringham.
His cancer was detected while he was undergoing treatment for an enlarged prostate in January. While the type of cancer has not been disclosed, the Palace confirmed it was not prostate cancer.
In the message of thanks, he wrote: "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 King has stepped back from all public-facing duties while he is being treated for the cancer, with senior royals - including Queen Camilla and the Prince of Wales - taking on his duties for some events.
He left Clarence House, London, for his Norfolk residence on Wednesday, accompanied by the Queen. His younger son, the Duke of Sussex, had flown in from the US for a brief visit earlier that day.
The Queen had said her husband was "very touched by all the letters and messages the public have been sending from everywhere".
Speaking at an event at Salisbury Cathedral on Thursday, she said the support had been "very cheering".
Prince William had also expressed gratitude for messages of support for his father and also for his wife, the Princess of Wales, as she recovers from abdominal surgery.
She is not expected to return to royal duties until after Easter.
This story was originally published by the BBC.