Prince Charles and Princess Diana's marriage was complicated, to say the least. The 14-year-long union was also filled with extra-marital affairs, and according to a former aide, the Princess of Wales was the first one to break her wedding vows.

It is popularly believed that Charles's fondness for his first love and his current wife, Duchess Camilla, was the biggest factor in the downfall of his marriage with Diana. Meanwhile, Diana also took on lovers during the later years of their unhappy marriage, most popularly starting an affair with British Army officer James Hewitt.

However, a former protection officer for the Princess of Wales has claimed that it was the Princess who first strayed in her marriage to Charles and had other love interests. Allan Peters claims that the Prince of Wales reignited his romance with Camilla only after he found out that his wife was having an affair with another protection officer, the late Barry Mannakee.

Peters added that it was him who informed Charles of Diana and Mannakee's relations. He claimed to CNN, "The popular perception is that the Prince of Wales was straying all the way through his marriage — and that is definitely, unequivocally, not the case. The first person that strayed was the Princess. He went back to see Mrs. Parker Bowles after he learned about her affair with Mannakee."

It is believed that Diana became involved with Mannakee during a fishing trip to Balmoral in 1985, four years after her wedding to Prince Charles and a year after they welcomed their second son Prince Harry. A year after their affair started, Mannakee was moved from Diana's protection team to the Diplomatic Protection Squad, where he died aged 39 in a crash.

Peters said about the relations between Diana and Mannakee, "I started to notice her behaviour was unusual whenever we were anywhere near Mannakee, so I decided to talk to her about it. For the first 20 minutes, she categorically denied it. But then she told me exactly what was going on: she was having some sort of relationship with Mannakee."

He added that when Charles inquired about Diana's behaviour, he told the royal that it would be better speak to his wife about it. In response, the heir apparent reportedly said, "Well, I've tried all that, and the only thing that seems to be upsetting her is that Barry Mannakee is going back to uniform. And, if she's that upset, Barry can stay."

Peters further revealed about his conversation with Charles, "At that stage, I was forced to say: 'Well, Sir, if he stays, then I'm afraid I'll have to leave.' And, I think, at that point the penny dropped. He was utterly shocked and was clearly very upset."

This version that Diana was the first one to be unfaithful in her and Charles's marriage was previously claimed by Jonathan Dimbleby in his authorised biography of Prince Charles published in 1994.

Princess Diana
25 October 1991: Princess Diana and Prince Charles are pictured looking unhappy during a visit to Toronto, Canada Tim Graham/Getty Images