The trouble started even before Charles and Diana's storybook spectacle of a wedding, according to reporter and biographer Sally Bedell Smith.

Prince Charles, it seems, had stumbled into the marriage. Press speculation of their affair had reached a fever pitch, prompting his father, Prince Philip, to advise either ending the relationship or proposing—pushing the heir to the British throne into the betrothal.

But the relationship was far from happy. Diana was paranoid that the Palace was trying to control her and that Charles was still seeing his former flame Camilla. On the way back from the second dress rehearsal of their wedding, Diana wept copiously in the car, Bedell Smith writes in her 2017 biography Prince Charles: The Passions and Paradoxes of an Improbably Life. By the honeymoon, the relationship had soured further—Diana would weep in her bedroom, and flounce out of dinner with the Queen and family, a shocking breach of protocol. Suffering from insomnia “and growing thinner by the day,” the princess showed increasing signs of eating disorders and tendencies for self-harm.

“‘What is it now, Diana?’ Charles would implore. ‘What have I said now to make you cry?’” reports Bedell Smith. “Again and again, he reassured her that his affair with Camilla Parker Bowles was in the past. He tried soothing Diana, but felt powerless to contain her emotional storms, which shocked him in their intensity and suddenness. At his wits’ end, he began seeking refuge in the Balmoral countryside with his paint-box, books, fishing rod and guns, but that only made his young wife even more aggrieved.”

Older mentors recommended Charles arrange psychiatric help, and even suggested valium—but Diana refused the drug, according to the author, “convinced in her growing paranoia that the Royal Family was trying to sedate her.”

Eventually a therapist, Dr. Alan McGlashan, was summoned, but Diana rejected him. Instead it was Charles who turned to him for help, and according to the author, Charles continued to see him for the next 14 years. “Charles’s friend Laurence Van der Post says McGlashan perceived Charles as ‘misunderstood and starved’ of ‘really spontaneous, natural affection,’ and provided the prince with ‘the respect his own natural spirit deserves.’”

The book goes on to detail the princess’s jealous rages and desire to pick arguments and fights. Bedell Smith says the prince told his cousin Pamela Hicks that “Diana would resurrect a row with him even when he was saying his prayers. She ‘would hit him over the head’ while he knelt.”

Previous accounts of Diana’s life have taken in her mental instability. In Andrew Morton’s famous biography (which Diana eventually admitted colluding in), Morton reports she attempted suicide several times and suffered repeatedly from bulimia, self-mutilation, depression and acute anxiety.

Bedell Smith lays the blame for both parties’ emotional inadequacies on their upbringings. “Diana was tormented by feelings of emptiness and detachment; she feared abandonment; she had difficulty sustaining relationships; and she kept those closest to her on tenterhooks,” writes Bedell Smith. “Ultimately, out of frustration, they abandoned her.”

Further revelations about Diana’s rages—which resulted in her throwing herself downstairs whilst pregnant, and slashing herself with razors, shards of glass and knives in front of her husband—paint a picture of a deeply disturbed woman, a long way from the ‘Queen of Hearts’ and ‘People’s Princess’ that was to become her legacy in the immediate aftermath of her death.

One of the prince’s former advisers tells Bedell Smith that after meeting Diana, he remembered thinking: ‘There is a rod of steel up this woman’s back.’ Diana’s father, Earl Spencer, later confirmed as much when he said: ‘Diana is very determined indeed and always gets her own way. I think Prince Charles is learning that by now.’

Diana’s hostility toward Charles is not spared by Bedell Smith. She hated all of his hobbies—his polo, his paintings, his gardening, even his love of Shakespeare—according to the author. “Diana taunted him by saying, ‘You’ll never be King,’ and banished many of his old friends—including the Romseys, the Palmer-Tomkinsons and the Tory MP Nicholas Soames. Resenting anything associated with Charles’s previous life, she also insisted on getting rid of Harvey, his yellow Labrador, who was sent to live with one of the prince’s advisers.”

Eventually, the couple took separate bedrooms. At Highgrove, Bedell Smith writes, "that entailed Charles moving into a dressing room to sleep on a single bed, along with a well-worn teddy bear,”

As a last attempt to facilitate reconciliation, the royal family sent in the Archbishop of Canterbury. But according to the author, he “saw ‘little evidence’ that Diana ‘was prepared to make the marriage work’ and concluded ‘with some sorrow that Charles was more sinned against than sinning.’”

When the Queen finally advised a separation, Bedell Smith says, “Everyone in Charles’s family took his side, including Princess Margaret, who had previously shown kindness, even tenderness, to Diana. Prince Philip sent his son a long letter, praising his ‘saint-like fortitude.’”

In separation, their relationship apparently mellowed, with Charles sometimes dropping in to see her and consulting her about their sons. But as Bedell Smith writes: “When Charles heard the news about Diana’s death while being driven through a Paris tunnel with Dodi, he was distraught. At 7:15 am, when his sons awoke, he told them what had happened.”

Later, lashed with grief, self-pity and regret, the prince turned to his courtiers. ‘They’re all going to blame me, aren’t they?’ he said plaintively.”