The king thanked the UK public for ‘the many messages of support and good wishes’ he’s been sent after receiving news of his ill health.
Charles has been spending time at his Norfolk residence of Sandringham since leaving Clarence House in London on Tuesday.
Buckingham Palace had announced the previous day that he was battling cancer, but did not confirm which type.
It’s the first time Charles has publicly acknowledged the diagnosis himself.
‘I would like to express my most heartfelt thanks for the many messages of support and good wishes I have received in recent days,’ His Majesty said.
‘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.
Speaking at a special ceremony to celebrate the work of charities at Salisbury Cathedral on Thursday night, she said: ‘He’s very touched by all the letters and the messages the public have been sending from everywhere – that’s very cheering.’
The couple were pictured in a car leaving the capital for Sandringham after Prince Harry’s fleeting 45-minute visit from the US.
Charles was seen waving and smiling to passers by despite his bad news.
His eldest son Prince William previously said the family was ‘grateful’ for the public support they have received in recent weeks.
‘We really appreciate everyone’s kind messages,’ he said at a London Air Ambulance charity event on Wednesday.
During a brief speech, he said: ‘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.
‘It means a great deal to us all.’
Buckingham Palace said a separate issue was ‘noted’ when the king underwent a recent hospital procedure for a benign prostate enlargement, and tests confirmed it was cancer.
The palace said Charles ‘remains wholly positive about his treatment’ and ‘looks forward to returning to full public duty as soon as possible’.
‘His Majesty has commenced a schedule of regular treatments, during which time he has been advised by doctors to postpone public-facing duties,’ a palace spokesman said earlier in the week.
‘Throughout this period, His Majesty will continue to undertake State business and official paperwork as usual.
‘His Majesty has chosen to share his diagnosis to prevent speculation and in the hope it may assist public understanding for all those around the world who are affected by cancer.’
William may step in to represent his father at an event, but no engagements are scheduled at the moment and the royal palaces will make arrangements if the need arises.
Kate also left hospital last Monday after abdominal surgery and returned to Adelaide Cottage in Windsor to be reunited with her three children, but the 42-year-old is not expected to return to official duties until after Easter.
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