Princess Diana and Princess Margaret had a cold war.

The late Princess of Wales shocked the members of the royal family when her secret interview was published. Princess Diana announced that her relationship with Prince Charles didn’t work because “there were three of us in this marriage” implying about his illicit affair with Camilla Parker Bowles. She also confirmed that she had an affair with James Hewitt.

According to the documentary “The Royal Family at War,” Princess Diana’s interview only worsened her rivalry with Princess Margaret who found her comments “unacceptable.”

Katie Nicholl said that Queen Elizabeth II’s sister never spoke with Princess Diana again after the interview. Royal biographer Andrew Morton said that the things between the two princesses quickly escalated into a “cold war” when both were still in Kensington Palace.

Princess Margaret reportedly told her staff to never talk to anybody from Princess Diana’s apartment. Ironically, Princess Diana used Princess Margaret’s door to let her boyfriend into the palace.

Princess Diana’s former butler Paul Burrell revealed that he used to sneak Dr. Hasnat Khan into the palace discreetly. He would pick him up at an agreed location and would cover him with a tartan rug as he lied flat at the back seat. The policeman on the gates usually just wave Burrell through, so their entrance was easy.

Then he would take him into Princess Margaret’s front door because it was the only place that didn’t have a CCTV camera.

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

Princess Margaret wasn’t the only senior royal who wasn’t happy with Princess Diana’s interview. Queen Mother was also “ deeply shocked.” She was devastated because she couldn’t comprehend the need for Princess Diana to open up about her troubled marriage to a biographer.

Queen Elizabeth II’s mother was sympathetic to Princess Diana and Sarah Ferguson because she understood the pressure of marrying the royal family. However, she still believed that “it is always a mistake to talk about your marriage.” Queen Mother lived her life based on obligation, discretion and restraint.

Princess Diana and Prince Charles
Princess Diana and Prince Charles at the Chelsea Flower Show, London, May 1984. She is wearing a navy maternity coat by Jan van Velden. Getty Images/Jayne Fincher