Prince William reportedly once broke up with Kate Middleton over the phone when they were dating and then got back together with her at a "naughty" costume party, a new book has claimed.

British journalist and royal biographer Robert Jobson discussed the ups and downs of Prince William and Princess Kate's relationship in his new biography, "Catherine, The Princess of Wales."

In an extract published by the Daily Mail, Jobson shared details about the Prince and Princess of Wales' brief breakup in 2007, three years before they got engaged.

According to the book, the couple's relationship was getting serious at the time, with Princess Kate being invited to attend Prince William's military graduation in December 2006.

However, when William suddenly canceled their plans for 2006 New Year's Eve, Middleton began to sense that "something was wrong," Jobson wrote.

Prince William, Kate Middleton
Prince Harry (L) and Prince William (C) and Kate Middleton (R) cheer on the English team during the RBS Six Nations Championship match between England and Italy at Twickenham on February 10, 2007 in London, England. Richard Heathcote/Getty Images

Middleton's hunch was apparently right as not long after, William called and broke up with her during "an emotionally charged 30-minute conversation," the biography stated.

Prince William reportedly told her that they "needed 'a bit of space' to 'find our own way'" and that he was "unable to promise her marriage," according to the royal author.

"It was a devastating blow to Catherine, who felt doubly let down at being dumped over the phone. Though it wasn't the first time William had called time on their relationship, it felt final," Jobson wrote.

After the breakup, Prince William went to Mahiki nightclub in London and "started yelling about being 'free,'" the book claimed.

Middleton, for her part, enjoyed trips with her mother and pals and partied at nightclubs with her sister Pippa in London in the months following the split.

Prince William ultimately regretted breaking up with Middleton and got the chance to woo her back at a "Freakin Naughty"-themed costume party.

Kate Middleton, Prince william and Zara Tindall
Catherine, Duchess of Cambridge, Prince William, Duke of Cambridge and Zara Phillips are seen during the Diamond Jubilee, Buckingham Palace Concert on June 04, 2012 in London, England. For only the second time in it's history, the UK celebrates the Diamond Jubilee of a monarch. Her Majesty Queen Elizabeth II celebrates the 60th anniversary of her ascension to the throne. Dave Thompson - WPA Pool/Getty Images

Middleton, who was dressed as a nurse, grabbed William's attention the moment he entered the party.

They reportedly spent the evening talking, dancing and eventually kissing before leaving the party together, according to the book.

Three years after they reconciled, Prince William and Princess Kate got engaged in 2010.

They wed in a lavish ceremony at Westminster Abbey in April 2011, and have since welcomed three kids: Prince George, 11, Princess Charlotte, 9, and Prince Louis, 6.

Kate Middleton, Catherine, Princess of Wales and Britain's Prince William
Britain's Catherine, Princess of Wales and Britain's Prince William, Prince of Wales embrace after attending The Royal Charity Polo Cup 2023 match at the Guards Polo Club in Windsor, west of London on July 6, 2023. Henry Nicholls/AFP via Getty Images

The royal couple -- who celebrated their 13th wedding anniversary in April -- previously opened up about their brief split during their 2010 engagement interview with Tom Bradby of ITV News.

"We both were very young, it was at university, we were sort of both finding ourselves as such and being different characters and stuff," Prince William said at the time. "It was very much trying to find our own way and we were growing up, and so it was just sort of a bit of space and a bit of things like that and it worked out for the better."

Meanwhile, Princess Kate admitted that she "wasn't very happy about it" but noted that the breakup made her a "stronger person."

"You find out things about yourself that maybe you hadn't realized, or I think you can get quite consumed by a relationship when you are younger, and I really valued that time for me as well although I didn't think it at the time. Looking back on it," she explained.

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Prince William, Kate Middleton