Princess Diana and Princess Margaret reportedly had a cold war several years ago. Their relationship worsened after the late Princess of Wales commented on her marriage to Prince Charles.

In the Channel 5 documentary “The Royal Family At War,” royal author Katie Nicholl said that Princess Diana’s statement about having three people in her marriage to Prince Charles was unacceptable for Princess Margaret.

After hearing the mom of two’s interview, Princess Margaret felt that Princess Diana went too far and decided to never speak to her again. Royal biographer Andrew Morton said that the two female royals’ relationship quickly turned into a cold war while they were still living in Kensington Palace.

“Princess Margaret would turn over any magazine that had Diana on the cover,” he said. “She told her staff not to talk to anybody from Diana’s apartments. It was a cold war,” Morton added.

Additionally, Princess Margaret reportedly watched Princess Diana’s every move whenever she had a boyfriend from behind the curtains. According to Morton, Princess Diana was actually aware that Princess Margaret was watching her.

“I had to deliver men to the Princess,” Morton said. “I had to bring them into clock court, which was immediately in front of Princess Margaret’s home and all the time the curtains were twitching. Margaret would be watching, keeping an eye on what Diana was doing and Diana would wave: ‘Hi, Margot, how are you?’”

Meanwhile, despite the two female royals’ complicated relationship, it was revealed that Princess Margaret actually empathized with Prince William and Prince Harry’s mom. In the book “Diana” by Sarah Bradford, the author said that this was because they were both rebels.

Princess Margaret saw a reflection of herself in the Princess of Wales. Princess Margaret also became a good friend to Princess Diana, and they got along well shortly after the latter joined the royal family. However, things only turned sour amid Princess Diana and Prince Charles’ divorce.

Princess Margaret passed away on Feb. 9, 2002, at King Edward VII’s Hospital, while Princess Diana passed away on Aug. 31, 1997, following a fatal car crash.

Princess Diana Picture dated 14 November 1992 of Princess Diana leaving the first anti-AIDS bookshop in Paris. Getty Images/Vincent Amalvy/AFP