Queen Camilla has spoken for the first time about King Charles III's cancer diagnosis, describing the pressure of keeping it secret in the early stages of treatment.

In a video to mark the 30th anniversary of Maggie's cancer charity, the Queen, who is president of the charity, recalls how "difficult" it was to avoid discussing her husband's treatment while on an official engagement with cancer patients and their families.

In January 2024, the Queen opened a new Maggie's cancer support centre at the Royal Free Hospital in London.

She had just found out that the King had cancer and would need treatment but had to hold back from telling anyone as the official announcement had not been made public.

"Nobody could say anything at the time, that was quite difficult.

"I almost said something but, you know, I felt that it wasn't the time to say," the Queen told the chief executive of Maggie's, Dame Laura Lee.

"It was just a week before it became public and the courage that must have taken for you," Dame Laura told the Queen - referring to how personally challenging the hospital visit must have been.

"I was just longing to let it out, but obviously I couldn't," the Queen said.

The King's cancer diagnosis was revealed on 5 February 2024, just days after the Queen's engagement at the Royal Free Hospital.

More than two years later, he is still receiving cancer treatment. Buckingham Palace has reiterated that his health continues to move in a "positive direction".

In the seven-minute film recorded at Clarence House, the Queen says the King's way of coping has always been to push on with official duties. She spoke of helping to look after her "poor husband".

"Nothing stopped him. He just said, 'This is my way. I'm going to cope with it,'" she said.

During the hospital visit, the Queen described feeling aware that she was now sharing the experience of so many families she met.

"I was almost questioning them. I didn't want to pry too deeply. But normally when I went in, I was just talking to them, but I don't know, I felt it was much more deep," the Queen said.

"I looked at everybody who was suffering and all the relations and I think it made me realise even more how important these places were."

The King has never disclosed the type of cancer he has, but has engaged widely with those treating and supporting cancer patients.

Maggie's says the King's public announcement prompted a 12% increase in men contacting them with a cancer diagnosis.

"The King's openness about his diagnosis has undoubtedly helped others to be more open themselves, and to now hear the Queen's completely understandable and natural response as a wife shines a light on why it is so important that family and friends also get the support they need," said Dame Laura.

"To hear her speak so powerfully of her own emotions when visiting the Royal Free centre, while knowing about his Majesty's diagnosis, is a huge honour."

Maggie's has 27 centres across the UK, built in the grounds of major NHS cancer hospitals, and supports hundreds of thousands of people each year.