The late princess called the confrontation the “bravest moment” of her marriage.

During her time as a working royal, the late Princess Diana was beloved by the public. Later known as “the People’s Princess,” Diana amassed a huge amount of love and support from many around the world, who quickly jumped to her defense when her husband, King Charles III (then, Princes Charles), had an affair with Queen Camilla (Camilla Parker Bowles at the time) throughout the course of their marriage. While Charles’ infidelity took a toll on Diana, she wasn’t afraid to stand up for herself. There was one particular moment of boldness—which her former protection officer, Ken Wharfe, witnessed and later reflected on in an interview with ITV—that she called “the bravest moment” in her marriage.

Per The Daily Mirror, Camilla’s sister, Annabel Elliot, was hosting a party, to which Diana received an invitation. No one expected Lady Di to show face, but she ultimately did. “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,” her former body guard recalled.

After an hour of enduring the awkwardness, Diana motioned for Wharfe to come to her assistance. “I went out, and there was Diana, who said, ‘You’ve got to come with me. I can’t find my husband or Camilla,’” Wharfe recounted. “Now, I couldn’t say no; clearly, this woman was in some distress, and eventually, we found the prince and Camilla [sitting] on a sofa in the basement of this property, just talking.”

Upon seeing the two of them cozying up together, Diana squared her shoulders and boldly confronted Camilla, which was the first time she had ever done so, according to the protection officer. “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,’” Wharfe continued.

Peter Macdiarmid / Getty Images

In response, Camilla had a quick comeback that hinted at the continuation of their affair, despite Diana’s knowledge of it. “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,’” the security guard said of Camilla’s remark. “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.” In 1992, just over a decade after their wedding, Charles and Diana separated, which eventually led to their final divorce decree in 1995. Two years later, Diana died in a car crash, and in 2005, Charles wed Camilla.

Charles and Camilla were reportedly romantically involved long before Charles married Diana—and allegedly even during her marriage to Andrew Parker Bowls, who she wed in 1973 and divorced in 1995. Although they broke things off, Diana always maintained that Camilla played too large a role in her husband’s life. “There were three of us in this marriage, so it was a bit crowded,” the late princess famously said in an interview with BBC’s Panorama.