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Inside the "Secret Pact" Between Princess Diana and Prince Philip

"The Duke of Edinburgh promised Diana he would do all he could" in regards to this one thing, an insider says.

Navigating relationships with in-laws can be tricky business, but for those who have married into the British royal family, it can become a veritable Game of Thrones situation. And that was exactly the case with Princess Diana. When she married Prince Charles in 1981, she had no idea that both Queen Elizabeth and Prince Philip knew of their son's enduring love for Camilla Parker Bowles, but encouraged him to go ahead with the wedding. When their marriage began to unravel, the princess hoped someone within the family would help her convince her husband to give up his then-mistress. Ultimately, she found a surprising ally: the Duke of Edinburgh.

In an unexpected show of support, Prince Philip wrote a series of letters to Diana in 1992 in which he reportedly offered to be the intermediary in an attempt to help her save her marriage. In one particularly telling missive, Philip wrote: "I can only repeat what I've said before, if invited, I will always do my utmost to help you and Charles to the best of my ability. But I am quite ready to concede that I have no talent as a marriage counsellor."

Another included this extraordinary revelation: "Charles was silly to risk everything with Camilla for a man in his position. We never dreamed he might feel like leaving you for her. I cannot imagine anyone in their right mind leaving you for Camilla. Such a prospect never even entered our heads." He closed the letter with: "With fondest love—Pa."

In his 2003 book, A Royal Duty, Diana's longtime butler Paul Burrell revealed Prince Philip was so intent on helping to keep Diana and Charles together, he even went so far as to make a numbered list of common interests and activities that could bridge the widening gap between them.

Princess Diana & Prince Philip in June 1986
Trinity Mirror / Mirrorpix / Alamy Stock Photo

The unusual correspondence between the princess and her father-in-law started after the publication of Andrew Morton's explosive book Diana: Her True Story (written with the princess's full cooperation in secret) in 1992. The correspondence started off as a torrent of criticism from the Duke, but eventually evolved into an unprecedented show of support.

"The Queen and the Duke of Edinburgh were deeply unhappy about the Morton book and Prince Philip was suspicious of Diana's cooperation, but of course, she denied it at the time," said my source. "Diana and Charles were summoned to a meeting at Windsor Castle with Her Majesty and the Duke. Afterwards, it was thought that now that everything was out in the open, they could find a way forward." When the princess failed to show up for the follow-up meeting, Philip fired off the first in a series of letters to Diana that, according to Burrell, "upset and infuriated" the princess due to the Duke's "brutal" comments.

In his book, Burrell recounts that Philip initially praised Diana for her royal tours and charity work, but chastised her, noting that being the wife of the Prince of Wales "involved much more than simply being a hero to the British people." Diana was crushed when Philip reportedly wrote that Charles had made "a considerable sacrifice" in giving up Camilla when he married her and that the princess had "not appreciated what he had done."

When Diana reportedly fired back with an angry response, Burrell wrote that the Duke responded with a letter that stunned her: "Phew!! I thought I'd gone a bit too far with the last letter…" From then on, the letters exchanged between the two took on a much softer and more supportive tone.

Prince Philip has never been one to mince words and has had a complicated relationship with Charles but, according to Burrell, the Duke's letters to Diana grew to be "understanding and sympathetic." They often spilled over into four handwritten pages, with Diana effusively thanking her father-in-law for helping her try to save her marriage.

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In 2018, excerpts of Diana's letters to Philip were published The Sun. Patrick Jephson, Princess Diana's private secretary at the time, told The Sun the Duke's letters meant a lot to her. "Here at last was written proof that this was acknowledged, recognised, and there was sympathy for her," he said.

"The Duke of Edinburgh promised Diana he would do all he could to help her save her marriage," said my source. "She thought of it as a secret pact between them. He persisted until it was clear there was nothing further to be done to keep Diana and Charles together. Diana never forgot the support she received from her father-in-law. She admired him greatly for his kindness during one of the most difficult times in her life." And for more on Diana, check out Here's the Truth Behind 17 Myths About Princess Diana.

Diane Clehane is a New York-based journalist and author of Imagining Diana and Diana: The Secrets of Her Style.

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