Princess Anne harboured deep resentment for Princess Diana and disliked her intensely ever since her first time in The Firm.
The princesses' frosty relations were detailed in Channel 5's documentary, Paxman on the Queen’s Children.
Royal expert Richard Kay said, "Princess Anne, she had no time for Diana.
"She didn’t like the way she went about her duty and the way she used the cameras and the media to promote herself, in her eyes.
"Anne had a much more traditional approach to monarchy and royal duty," Kay added.
The programme's presenter, former BBC journalist Jeremy Paxman, said Anne disapproved of Diana's modern outlook.
"Diana and Fergie were much better at appearing human. Dedicated and hard-working Anne was most rapidly eclipsed. Diana made her look out of touch," Paxman shared.
Moroever, Diana did not attend Anne's daughter Zara Tindall's christening ceremony, which further worsened their ties.
"She had been telling friends beforehand that she had no intention of going but, rather through a failure of manners or courage, it was not until 48 hours before the actual ceremony that she telephoned Princess Anne to inform her that she would not be there," royal author Ingrid Seward said, "The tone of Anne’s response would have chilled the Arctic."