Queen Camilla said King Charles is “doing very well under the circumstances” after beginning cancer treatment.
In response to a question about the king’s condition during an event held at Salisbury Cathedral on Thursday evening, she said: “He was deeply affected by all the letters and messages sent by the public from everywhere.”
“This is very exhilarating,” she added.
Buckingham Palace announced the king's cancer diagnosis on Monday.
The palace said it was discovered while the king was undergoing treatment for an enlarged prostate last month. The type of cancer was not revealed, although it was confirmed that it was not prostate cancer.
The palace said the king had withdrawn from all his public duties while undergoing treatment. Senior members of the royal family, including the Queen and the Prince of Wales, will officiate at some events.
On Wednesday, the royal was photographed for the first time since his diagnosis was announced alongside the queen in a car leaving Clarence House in London to catch a helicopter to Sandringham in Norfolk.
Buckingham Palace said the king would continue with his paperwork and constitutional duties during the indefinite treatment period.
Before the King left London, his son, the Duke of Sussex, traveled from the United States to visit him. He was seen at Heathrow Airport the next day returning to Los Angeles, where he lives with his wife, Megan, and their two children.
The Queen was speaking on Thursday evening at a concert celebrating the work of local charities at Salisbury Cathedral in Wiltshire.
Among those I spoke to was a member of the Wiltshire Air Ambulance team, Paramedic Ben Abbott, who said: “I hope His Majesty is doing well ma’am, we are all really sad to hear the news.”
Abbott, who is aware the Queen has a home in the Wiltshire village of Lacock, added: “I told her we always wave when we fly over Lacock, and she said she always waves back.”
Other members of the royal family have also continued to carry out their royal duties since the King's health was announced.
On Wednesday, the Prince of Wales attended a fundraising event for the London Air Ambulance.
During the ceremony, he expressed his gratitude for the “kind messages” of support from both the King and his wife, the Princess of Wales, who is recovering from abdominal surgery.
Earlier in the day, he held an investiture ceremony at Windsor Castle. His return to public duties came after a three-week absence that began after Catherine underwent surgery.
She is not expected to return to her royal duties until after Easter.
The Princess Royal also attended official engagements on Wednesday, but Anne did not respond to questions about the royal when asked by reporters as she left a military barracks in Bicester, Oxfordshire.
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