He features in a documentary by former ITN newsreader Mark Austin, whose own daughter had a devastating battle with anorexia.
William, 35, wrote to Austin after reading a newspaper article about his anguish at being unable to cope with his "dangerously ill" daughter, Maddy, 22, and the family’s struggle to get help for her.
In his letter, William praises Austin’s "bravery" and says the article moved him. The Channel 4 documentary, Wasting Away: The Truth About Anorexia, shows William talking to Austin and Maddy at Kensington Palace about Princess Diana’s illness.
Austin and his daughter are seen watching the princess’s 1995 BBC interview with Martin Bashir in which she talks about the break-up of her marriage to Prince Charles and how her lack of self-esteem led to a battle with bulimia.
She says: "I had bulimia for a number of years, and that’s like a secret disease. It’s a repetitive pattern which is very destructive. It was my escape mechanism."
William and Prince Harry have dedicated their public roles to breaking the stigma around mental health. But the princes have not directly tackled their mom’s eating disorder.
William tells Austin and his daughter, who has now recovered: "We need to normalise the conversation about mental health. The fact that you are speaking out is incredibly brave."
When Maddy tells him: "I was inspired by what your mom did," William replies: "We need to be matter-of-fact about it, and not hide it in the dark"
Austin said it was "amazing" Di spoke out on the issue 22 years ago.Daily Mail