By Jennifer Davis
Updated Aug 22, 2017 @ 7:15 pm

Prince William is opening up about his mother Princess Diana's eating disorder—and how she inspired others by sharing her story—for the first time ever.

In the new documentary Wasting Away: The Truth About Anorexia, William gets candid about her struggle with bulimia and mental health with British news anchor Mark Austin, who was inspired to create the documentary after his daughter Maddy dealt with anorexia.

Prince William and Princess Diana Lead
Credit: Tim Graham/Getty

During the conversation with Austin and Maddy, he once again reiterates the importance of talking about mental health, something that his organization Heads Together has been striving to do. "We need to normalize the conversation about mental health," he said during their discussion. With this documentary, both Austin and Maddy are able to do just that. "The fact that you are speaking out is incredibly brave," William continued.

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Maddy's bravery comes in part thanks to Diana, who she says helped her by going public with her own struggles with an eating disorder. “We need to be matter-of-fact about it, and not hide it in the dark where it festers," he said after she told him how his mother helped her.

"These are illnesses,” he said. “Mental health needs to be taken as seriously as physical health.”