Prince William broke up with Kate Middleton over the phone in 2007, royal expert reveals.

Prince William is reportedly more protective of Princess Kate than ever following her cancer diagnosis and ongoing preventive treatment, but it hasn't always been rainbows and sunshine for the married pair.

According to royal expert Robert Jobson, Prince William, who is preparing to release a new biography on Catherine, the Princess of Wales, has called Kate Middleton to say goodbye.

Prince William called Middleton to say goodbye in 2007 after canceling plans for New Year's Eve, US Weekly reported, according to the upcoming biography.

"Seemingly out of the blue, William called to say goodbye and told her that he felt they needed to 'put some distance' between them in order to 'find their own way,'" Jobson wrote, while also noting that at the time, both Middleton and Prince William were "on 'different page,'" he added.

"William's admission of his inability to commit to the marriage deepened Catherine's disappointment and sense of loss," Jobson wrote in the book.

"It was a devastating blow to her longtime companion. She also felt disappointed in William's decision to handle the situation over the phone rather than face to face."

[10

Jobson claims that the 2007 phone call and subsequent breakup "was not the first time William had put an end to their relationship, but this time was different and more definitive than usual."

The two first met and began dating in 2001; in 2004, according to Jobson, they "temporarily broke up"

due to their "youth."

Jobson claims that the 2007 breakup was difficult for Princess Kate. Princess Kate was not "expecting an immediate proposal or engagement ring," but wanted "some form of greater commitment."

Prince William eventually proposed to Middleton on November 16, 2010, and they walked down the aisle on April 29, 2011.

According to a recent report in the Mirror, the Prince waited to propose because he was "acutely aware of the stress of being tied to the royal family and wanted to give her the chance to 'back out' if she felt she could no longer endure life as queen."

"I wanted to give her a chance to see how she was doing and to step aside if necessary before everything got out of hand," Prince William told ITV's Tom Bradby in an interview shortly after the engagement.

"I'm trying to learn from the lessons of the past.