Princess Diana denied having anything to do with author Andrew Morton‘s explosive 1992 tell-all about her failing marriage to King Charles III and misery as a member of Britain’s royal family.

But one senior royal wasn’t buying it.

According to excerpts from Hugo Vickers‘ upcoming biography, Queen Elizabeth II, which was recently serialized in Daily Mail, Queen Elizabeth II‘s husband, Prince Philip, came to his own conclusion about Diana’s involvement in the bestseller initially published under the title Diana: Her True Story.

As Vickers writes, “It seems almost incredible that so many people accepted Diana’s denial of any involvement in the book.”

“One person who wasn’t fooled, though, was Prince Philip, who read the book on flights to and from Canada in July [1992] and clearly detected her hand in it. Feeling that too much had been revealed, he was not impressed.”

The falloutIn a new royal biography, Hugo Vickers writes that in cooperating with author Andrew Morton, Princess Diana ‘laid every grievance she could muster against her hapless husband,’ King Charles III, and confirmed that the former Camilla Parker Bowles was ‘the other woman in his life.’ By: Phil Loftus/Capital Pictures / MEGA

In a new royal biography, Hugo Vickers writes that in cooperating with author Andrew Morton, Princess Diana ‘laid every grievance she could muster against her hapless husband,’ King Charles III, and confirmed that the former Camilla Parker Bowles was ‘the other woman in his life.’ By: Phil Loftus/Capital Pictures / MEGA

The book delivered a “hammer blow” to the then-Prince and Princess of Wales’ already fragile marriage, Vickers explains.

It detailed Diana’s deeply personal struggles — including the breakdown of her relationship with the future king and his intimate relationship with Queen Camilla, who at the time was still his married mistress, Camilla Parker Bowles — which intensified scrutiny of the royal family.

Behind palace doors, tensions were high.

Vickers recounts a “sticky meeting at Windsor” where Diana and Charles sat down with the queen and Duke of Edinburgh to address the growing crisis.

During the discussion, Diana maintained that Charles had never wanted to marry her and that the situation with Camilla had become “intolerable.”

While the monarch “maintained her neutrality,” Vickers writes, Philip took a more active role.

Trust erodesAuthor Andrew Morton wrote the international bestseller ‘Diana: Her True Story: In Her Own Words,’ which exposed Princess Diana’s isolation, bulimia and the collapse of her marriage, altering public perception of the British monarchy. By: MEGA

Author Andrew Morton wrote the international bestseller ‘Diana: Her True Story: In Her Own Words,’ which exposed Princess Diana’s isolation, bulimia and the collapse of her marriage, altering public perception of the British monarchy. By: MEGA

In the months that followed, Philip attempted to intervene privately, writing a series of letters to Diana between June and October 1992 in hopes of helping salvage the marriage.

According to Vickers, who has read their correspondence — Philip penned six letters, Diana wrote five — the exchanges revealed how invested the Duke of Edinburgh was, with Diana acknowledging that it was clear he “really cared.”

But his efforts were complicated by growing mistrust.

Vickers writes that Philip became uneasy after recognizing “one or two phrases from his correspondence with Diana popping up in the press.”

It raised alarm bells. “This made him worry that every time there was a private discussion between Charles and Diana, details would appear in the Daily Mail,” Vickers writes.

Tragedy and vindication

Charles and Diana publicly announced their separation at the end of 1992. Their divorce was finalized in 1996.

Although Diana had denied working with Morton, the full extent of her involvement eventually became public.

As noted in Vickers’ book, the truth emerged shortly after she tragically died in 1997.

“Within a month of Diana’s death, Andrew Morton exposed to the world the full extent of her cooperation with his book,” Vickers writes. “Prince Philip had been right all along.”

Morton republished the bestseller with a new title — Diana: Her True Story: In Her Own Words — in October 1997, just weeks after the 36-year-old princess was killed in Paris.

This version contained transcripts of the tapes she’d recorded answering Morton’s questions, which were relayed via her friend Dr. James Colthurst, who served as an intermediary.