Princess Diana reportedly leaked Sarah Ferguson and Prince Andrew’s separation to the press at a time when it was still supposed to be kept a secret.

In the Channel 5 documentary “Royals At War,” biographer Andrew Morton recounted how a furious Princess Diana became visibly upset when she found out that a rival book by Ferguson will be released weeks before her own.

“Diana was incandescent, how do we get this off the front pages? I said to her, ‘Look, the only way you’re going to do it is to have another fact,’” Morton said.

The Princess of Wales then told Morton that the Duke and Duchess of York were just at Sandringham to talk to Queen Elizabeth II regarding their separation. Morton told the mom of two that the couple’s separation is a fact, and he decided to write about it.

Immediately after the news about the royal separation broke, Ferguson received flak from Her Majesty, who seemingly thought that it was Prince Andrew’s ex-wife that leaked the information to the media.

In the book “The Diana Chronicles,” author Tina Brown said that the monarch was personally infuriated by the leak. As such, it resulted in the Queen and the royal household cutting ties with Ferguson.

Even though Ferguson went through a difficult time post-separation from Prince Andrew, she never once suspected that the leak came from Princess Diana. After all, she considered Princess Diana as her best friend.

But according to royal editor Robert Jobson, Princess Diana might not have felt the same way about Princess Beatrice and Princess Eugenie’s mom.

“Diana was quite calculating when it came to Fergie on occasion,” he said. “I remember Diana was going to be offered a new car, and she said, ‘I’ll let Sarah try that out first so I can see what the reaction would be.’”

Jobson said that Princess Diana used Ferguson as a bit of a yellow canary so that when things go wrong, she could step away from the situation and Ferguson would get all of the criticisms and bad publicity.

Princess Diana and Ferguson stopped talking to each other, and they were not in good terms when the former died in 1997.

Princess Diana Princess Diana wearing a Jasper Conran suit during a visit to a community center in Brixton, October 1983. Princess Diana leaked Sarah Ferguson's separation from Prince Andrew because she wanted to make sure the attention of royal fans won't be directed at the Duchess of York's book. Getty Images/Princess Diana Archive