Princess Diana and Prince Philip used to write letters to each other before the former divorced Prince Charles. During one of their correspondence, the late royal acknowledged the fact that she and her father-in-law didn’t always see eye to eye.

On one occasion, the mom of two told the Duke of Edinburgh that it’s great to see that their letters are getting shorter and shorter. For the late royal, this meant that they were finally understanding each other more and more.

Prior to this, the royals’ correspondence was filled with surprising statements. For instance, the retired royal once told Prince Charles’ ex-wife that he never dreamed that his eldest son would leave Princess Diana for Camilla Parker Bowles.

“I cannot imagine anyone in their right mind leaving you for Camilla. Such a prospect never even entered our heads,” he wrote.

On another occasion, Prince Philip told Princess Diana that he had no talent as a marriage counselor. And he also encouraged Prince William and Prince Harry’s mom to contemplate the real reason why the heir to the throne chose to end their marriage.

“Charle’s relationship with Camilla had nothing to do with your behavior towards him in your marriage,” he wrote.

In the Channel 5 documentary “Images of Diana,” royal author Sarah Bradford said that Princess Diana was quite close to her father-in-law. And Prince Philip was also very fond of the Princess of Wales. In fact, he encouraged the late royal to call him “pa.”

“He really wanted to keep things together and so did the Queen…They didn’t like Camilla and Charles carrying on a relationship which endangered the monarchy,” she said.

Meanwhile, royal author Angela Levin wrote in the book “Harry: Conversations With the Prince” that Prince Charles also found his dad’s support during one rare moment while he was going through his separation from Princess Diana.

The Duke of Edinburgh wrote a letter to his eldest son saying that he had the fortitude of a saint for putting up with Princess Diana.

Prince Philip, Queen Mother, Princess Diana, Queen Elizabeth, Prince Charles, Prince William
Pictured: Prince Philip, Prince Charles, Queen Mother, Princess Diana with Prince William and Queen Elizabeth II at Buckingham Palace. Getty Images/PA