Inside Kate Middleton, Prince William's brief break up and reunion

 Kate Middleton and Prince William’s relationship almost never happened.

In William and Catherine, The Monarchy’s New Era: The Inside Story (out March 10), author Russell Myers shares insight into the couple’s journey using 100 interviews about their private turning points.

"Now was the right time to provide a definitive account of William and Catherine’s life together," Myers told People. "They are pillars of the modern monarchy."

The couple famously met at the University of St. Andrews and almost broke up in 2007. According to Myers, Queen Elizabeth intervened and gave William the push that was needed for him to commit to Kate.

The Queen, was was impressed by Kate, "could see [Kate] had all the qualities of a future Queen," Myers told the the outlet, adding that her conversations with the future King became the "catalyst for William changing course" and recognizing that "if he had faith in the relationship and his love for her, then that would be enough to carry them through."

In an excerpt obtained by the outlet, the author pulls back the curtain on the couple’s 2007 fall out.

After the couple suffered a rough patch, "Catherine delivered an ultimatum to William."

"Catherine was distressed. She was miserable, but she certainly wasn’t desperate. She felt as though she had nothing to lose and for the first time she probably relayed her true feelings to William. She wasn’t demanding an engagement, but she wanted a commitment," added Myers.

"Blinded by his own insecurities, William did not react in the way Catherine expected. In a subsequent 30-minute phone call he laid out his reasons for believing they were on 'different pages' and said he could not offer her a guarantee of marriage. Catherine was understandably devastated. The couple agreed to give each other the space they needed. Secretly, Catherine wondered whether she would ever see William again . . . It’s telling that William confided to one senior courtier that, 'at least she is free,'" he continued.

It was then that the late monarch stepped in, and shared wise advice with William.

Myers wrote, "Sensing William was struggling, the Queen invited him to Sunday lunch to judge his mood. William was more than just crestfallen and worried about whether he was throwing away the one constant in his life. He was, according to one well-placed source, completely broken. 'In that moment the Queen advised her grandson that the only certain path is the one supported by faith. It was all she had to say,' the source said."

William decided to make his move. At first, he texted and asked to speak, wondering if Catherine would even reply. With Catherine unsure of William’s motives and unwilling to let her guard down just yet, the initial exchanges were tentative, if a little frosty. William explained that he was missing her and floated the idea of them still attending a party that had been in their [calendar] for months.

William then reached out and arranged to meet at a party.

At the party, "Fellow guests said as soon as William and Catherine set eyes on one another it was clear their love had not extinguished."

He continued, "The couple peeled off from the rest of the party and spent hours locked in deep conversation. Catherine listened intently as William attempted to break the deadlock, laying out his reasons for doubting what they had. He talked of his fear of letting someone truly experience the world in which he lived, and also his fear of rejection if he did let himself get too close. Catherine, of course, knew that she still loved William deeply. That was why she had been so explicit in her demands. She was willing to agree to a future, if only he would stop allowing outside factors to affect his judgement. After speaking for what seemed like hours, William’s charm, it seemed, had worked. The couple returned to the party. As the cocktails flowed and the dance floor filled, they only had eyes for each other."

Prince William and Princess Kate got married in 2011 and share three kids: Prince George, Princess Charlotte, and Prince Louis.