The King has offered his “most heartfelt thanks” to the public for their support after his cancer diagnosis, saying their kind thoughts are the “greatest comfort and encouragement”.

In his first public comments acknowledging his illness, the King recognised the goodwill he has been shown since Buckingham Palace announced his diagnosis less than a week ago.

Writing from Sandringham, Norfolk, where he is working from home and resting after his first bout of treatment, the King spoke of his “lifelong admiration” for all those who support cancer patients.

It is “all the greater”, he said, now that he has experienced their care personally.

The King is undergoing treatment for an unspecified cancer, and will be spending most of each week at Sandringham or Highgrove away from public engagements to protect his health.

He is expected to return to London more or less weekly to hold his audience with the Prime Minister and receive further treatment and medical advice.

In his message to the nation, the King 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.