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Prince William and Kate Middleton have been a couple since their school days, but the road to their engagement has been a rocky one, with William breaking up with Kate in 2007.
Christopher Andersen, author of William and Kate: A Royal Love Story tells ET, "She expected him to propose to her when he broke up with her. It came at a particularly sensitive time. William had just graduated from Sandhurst Military Academy and entered training for the army; she had to fend for herself with the paparazzi in London.
In his new book about the royal couple, in stores Tuesday, Dec. 21, Andersen says that William split with Kate over a cell phone.
"She was at work when she got the call," Andersen says. "Basically, he said, 'It's not fair to you.' … She did not want to break up and she was very hurt. She was devastated. A friend said she was crushed. At one point -- and this is very uncharacteristic because she didn't talk about her private life -- Kate said, 'It's his daddy,' and explained that, in fact, Prince Charles was behind the breakup."
Andersen says that William had been advised by his father not to string Kate along, to break up with her if he wasn't ready to marry her.
The breakup only lasted six weeks, but Andersen says that the tensions reportedly started with the rumored revival of William's relationship with his ex-girlfriend Jecca Craig, who became close to the prince during the year he spent in Africa. In fact, Andersen writes that William had actually proposed to Jecca.
"At one point Kate, actually did confront William," Andersen says. "She didn't want him to visit Jecca alone in Africa. It didn't look good as far as Kate Middleton was concerned and she said, 'It has got to stop.' He, using one of Prince Charles' phrases, said, 'Don't tell me what to do. I'm going to do what I want to do.'"
While Kate was nursing a broken heart, she put up a brave front; going so far, according to Andersen, to win back her prince by making him jealous.
"She joined an all-female rowing team called 'The Sisterhood' and they trained to race across the English Channel," Andersen tells ET. "She was working out more. She lost some weight."
Then, Kate and her sister Pippa hit the London clubs, and Kate began dating some of the most eligible men in England. Her plan was working.
"William knew most of these guys and became very jealous very quickly," Andersen says.
The prince's response, according to the author, was to drown his sorrows.
"William went on a drinking binge with his buddies," Andersen says. "As a matter of fact, on one night alone, he spent $17,000 on Dom Perignon for his group of friends at a club called Mahiki, which was his favorite hangout."
Truth be told, today William and Kate's engagement may mean so much because their breakup was so public. In a recent interview, they set the record straight.
Prince William said, "We did split up for a bit… It was very much trying to find our own way and we were growing up, so it was just sort of a bit of space and a bit of things like that and it seemed to work for the better."
While Kate commented, "At the time, I wasn't very happy about it but actually it made me 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're younger, I really valued that time."
William and Kate: A Royal Love Story will be in stores on Tuesday, Dec. 21.