Princess Diana confronted Camilla and gave her a 12-word warning after finding her with Prince Charles after they snuck off together at a party, a former royal protection officer has claimed.
Diana married the heir to the throne in a fairytale wedding at St Paul's Cathedral more than 41 years ago - with the couple having sons Princes William and Harry.
But it was later revealed that Charles had been unfaithful to his wife with the then Camilla Parker Bowles - a former girlfriend who he had dated in the 1970s.
This led to his Diana saying in her bombshell Panorama interview: "Well, there were three of us in this marriage, so it was a bit crowded."
And now former royal protection officer Ken Wharfe, who was part of Diana's security team for six years, has revealed the moment the royals realised the end was nigh for their marriage.
Speaking to Ranvir Singh on ITV's Lorraine programme today, he recalled how Diana and Charles attended a party being thrown by Camilla's sister - and that Camilla was there.
He told how he and others were surprised Diana went to the party, given it was full of people who were close to Camilla and Charles.
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Mr Wharfe said: "Diana didn't have any particular friendships at that party but when we arrived there, it was almost like freeze-framing a scene in a movie because there was this surprise that Diana had even arrived.
"But then soon after within the hour, I heard my name being called, I was in the kitchen somewhere. And I went out and there was Diana, who said 'you've got to come with me, I can't find my husband or Camilla'.
"Now, I couldn't say no, clearly this woman was in some distress, and eventually we found the prince and Camilla sat on a sofa in the basement of this property just talking."
Mr Wharfe added that he didn't quite know what was going to happen next, but Diana delivered her warning.
He explained: "I didn't know quite what Diana was going to do at that point but with a great deal of confidence, Diana just went up to both of them and said to Camilla 'please don't treat me like an idiot, I know what's going on'.
"And Camilla sort of said something, to which still to this day I have never really understood what she meant by that is 'well you know, you have two wonderful boys'.
"Well, it was an incredible moment for me and certainly for them as well. That was a defining moment in their life because I think at that point... this was an indicator the end was nigh."
Mr Wharfe's chat on Lorraine comes as he prepares to launch a new book, Diana Remembering the Princess, which marks the 25th anniversary of her death.
After Charles and Diana split in 1992, they eventually divorced four years later in 1996.
However, just a year later, Diana died following a tragic car accident in Paris at the age of 36.
Charles then married Camilla in 2005 and she became the Duchess of Cornwall. When the Prince of Wales takes the throne, his wife will be known as Queen Consort.
