The Queen wrote a letter to Princess Diana just weeks after she gave a tell-all interview on the breakdown of her marriage to BBC Panorama.
In the interview, which was watched by 22.8 million people, Diana famously told interviewer Martin Bashir there were "three of us" in her marriage to Prince Charles - referencing his love for Camilla.
As well as stating the monarchy was in desperate need of modernisation, Diana described the prince's camp as the "enemy".