According to royal biographer Robert Jobson in his latest book Catherine, the Princess of Wales, “among the student community, it was an open secret that they were a couple”. However, it was one of William’s former girlfriends who officially spilled the beans about the couple.

Kate Middleton

Kate Middleton started dating Prince William while at university

Jobson said it happened during a “revealing moment” at a dinner party attended by friends of William and Kate, including his ex Carly Massy-Birch. Massy-Birch, “perhaps unwittingly” revealed William’s secret relationship with Kate during a spirited game of ‘Never Have I Ever’, “much to the prince’s chagrin,” Jobson alleged.

He referenced royal writer Katie Nicholl and her 2013 book Kate: The Future Queen. One partygoer explained to Nicholl: “[Carly] announced, ‘I’ve never dated two people in this room’, knowing full well that William was the only one who had because Kate was sitting next to him.”

This revelation stunned all in attendance. Prince William’s reaction was terse as he “shot a thunderous look” at his former flame and is said to have muttered: “I can’t believe you just said that.

Prince William

It was his ex-girlfriend who revealed all

One insider said it was the first public acknowledgment of William and Kate’s relationship. “We knew they were together, but it was the first time William confirmed his and Kate’s relationship in public,” they said.

Despite the uneasy moment, it appears there were no hard feelings between William and Carly, as she joined the celebration of William and Kate’s marriage in April 2011.

Later, Carly reminisced with Nicholl about her fleeting fling with William, admitting: “We got on well, but I think we would have got on well even if nothing had been going on romantically.” She admitted she considered it a typical university romance.