Camilla said her husband, who has undergone his first bout of cancer treatment earlier this week, was “very touched” by all the messages of support he has been receiving from the public.

Charles has been spending his time at Sandringham following his diagnosis which was announced by Buckingham Palace on Monday.

He hosted a whirlwind visit from his son the Duke of Sussex on Monday and the royal family have received many messages of support from the public during royal events over the past few days.

The Queen left Charles at Sandringham to fulfil her royal engagement at Salisbury Cathedral and among the first people she met were medical staff from Wiltshire Air Ambulance.

Ben Abbott, 40, a critical care paramedic, said: “I do hope His Majesty is doing well Ma’am, we’re all really sad to hear the news.”

Camilla replied: “Well he’s doing extremely well under the circumstances, he’s very touched by all the letters and the messages the public have been sending from everywhere – that’s very cheering.”

Charles has postponed all public-facing duties, but is continuing with behind-the-scenes work on his red boxes of state papers.

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 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.

The Queen has a home in Lacock, Wiltshire, and she chatted with the air ambulance medics about their work.

Mr Abbott said: “I told her we always wave when we fly over Lacock and she said she always waves back.”