After her last stand-off with her husband in the media, Diana felt some irretrievable damage had been done. She kept asking one of her aides “What have I done? What have I done to my children?”

Prince William and his younger brother Prince Harry tragically had a front row seat into their parents’ divorce battle.

From the separation in 1992 to the finalisation of their divorce in 1996, public feuds between Princess Diana and the then Prince Charles had William and Harry at the centre of their parent’s misery. After Charles admitted to his relationship with his Camilla in 1994 in a TV interview with Jonathan Dimbleby, it was Diana’s turn to reveal a secret. It was William’s mother’s candid admission that there had come to be four in the marriage — and she’d fallen in love with James Hewitt — which tipped the teenager over the edge.

At just 13 years old William saw Diana make her final checkmate move in her media battle with his father. In her November 1995 interview with Martin Bashir on BBC’s Panorama, which William watched alone in his housemaster’s study, Diana talked of ‘three of us in this marriage’. Harry and William had spent long hours on horseback with the man they’d called Uncle James and had driven down with him and Diana quite regularly to stay in Devon for breaks with his mother Shirley.

Diana spoke of ‘betrayal’, after Charles revealed his relationship with Camila, but that’s also exactly what William felt when his mother revealed her relationship. Diana had known of the Prince’s upset when Charles had confessed his intimacy with Camilla on TV. Yet she did the very same thing. When William’s housemaster returned to his study, he found the prince slumped on the sofa, his eyes red with tears. And when Diana telephoned an hour later, William refused to speak to her.

Two days later, the distraught princess told her faith healer Simone Simmons what had happened. Diana had said: that William had been “so angry with her,” that he’d broken out in rage. ‘All hell broke loose. He was furious . . . that she had spoken badly of his father, that she had mentioned Hewitt . . . He started shouting and crying and, when she tried to put her arms around him, he shoved her away.’ Whilst William did apologise to his Diana the next day and gave her flowers, Diana felt some irretrievable damage had been done. She kept asking Simone: “What have I done? What have I done to my children?”