It was one of Kate’s ex-girlfriends, Carly Massy-Birth, who revealed that Prince William was dating Kate Middleton during the confession-like drinking game, said royal biographer Robert Jobson.

Prince William, and Kate Princess of Wales on the balcony of Buckingham Palace with their children Prince George, left, Prince Louis, front centre, and Princess Charlotte wave to the crowds after the Trooping the Color ceremony, in London(AP)

Kate Middleton and Prince William had tried their best to keep their romantic life away from the spotlight for a long time. However, their attempts fell short at a dinner party where the duo was forced to admit their love affair due to a drinking game.

According to royal biographer Robert Jobson’s new book, ‘Catherine, the Princess of Wales’, the couple had attended a dinner party with their friends when those in attendance decided to participate in the popular drinking game ‘Never Have I Ever’.

It was one of Princess of Wales’ ex-girlfriends, Carly Massy-Birth, who revealed that Prince William was dating Kate Middleton during the confession-like drinking game, said Jobson in his book.

In his biography, Jobson, according to People, wrote: “Perhaps unwittingly, Carly exposed William’s secret love affair with Catherine, much to the prince’s chagrin.”

The royal couple first encountered each other in 2001 at St. Andrews University in Scotland. Popular rumors suggest that William captivated Middleton by purchasing a £200 front-row seat to observe his future wife on the runway at a charity fashion show.