Andrew Morton Reveals How Princess Diana's Secret Tapes Helped Him Tell Her Story 

Princess Diana’s voice is being heard once again — 25 years after her death.

DIANA: Her True Story – In Her Own Words, author Andrew Morton revisits the extraordinary saga that led to the bombshell biography’s original publication in 1992.

To the rest of the world, Diana’s life seemed a fairy tale, with her marriage to Prince Charles at the heart of it. The reality, of course, was very different — and Morton’s book was a way to reveal “the unvarnished truth,” as the author writes a new foreword, which is excerpted exclusively in this week’s PEOPLE.

Feeling trapped by royal life, angry about her husband’s affair with the then-Camilla Parker Bowles and desperately wanting to ensure the public heard her side of the story, Diana recorded her innermost thoughts on a series of audiotapes beginning in May 1991. Her friend, Dr. James Colthurst, then delivered the tapes (by bicycle) from Kensington Palace to Morton, a U.K. newspaper journalist.

RELATED: Five Things To Know About Princess Diana and Prince Charles’ Strained Relationship

Morton took the tapes to a café, where he listened as Diana unspooled her secrets, including her battle with bulimia and her thoughts of suicide.

“It was like being transported into a parallel universe, the Princess talking about her unhappiness, her sense of betrayal, her suicide attempts and two things I had never previously heard of: bulimia nervosa, an eating disorder, and a woman called Camilla,” Morton writes.

Diana wrote to Colthurst six months before the book was published and spoke about her anticipation of the storm that would surely come upon its release, but also, her relief at finally having her story out in the world.

“Obviously we are preparing for the volcano to erupt and I do feel better equipped to cope with whatever comes our way!” she wrote in the letter, which Morton cites in the updated biography. “Thank you for your belief in me and for taking the trouble to understand this mind—it’s such a relief not to be on my own anymore and that it’s okay to be me.”

Upon the book’s publication in 1992, Diana’s participation remained a secret. But after her death in a 1997 car crash, Morton revealed that she had been his true source, along with members of her inner circle who had spoken at her behest.

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