Prince William reportedly left Kate Middleton miserable after their short split.

In Jessica Jayne's book "The Duchess of Cambridge: How Kate Middleton Became A Future Queen," the author covered the Duke and Duchess of Cambridge's "trial separation." According to Jayne, Middleton was furious when Prince William decided to take off on an all-boys holiday with his friend Guy Pelly, an acquaintance that Middleton "never thought highly of."

The Duchess of Cambridge saw Pelly as a "bad influence" to the duke. She was left miserable when she found out that Pelly hired an all-female crew for their trip away.

In response to their separation, Middleton reportedly packed her bag and returned home to Berkshire. She spent the summer with her family.

While Prince William was away, Middleton "let her guard down" around her friends. The now royal mom was torn whether she reach out to the Duke of Cambridge or not.

"She got quite drunk on white wine and really let her guard down. She was debating whether or not she should text or call him," one of Middleton's friends said. "She said how sad she was and how much she was missing William but she never mentioned it after that."

According to Jayne, Prince William and Middleton's trial separation was due to the former's desire for space. Also, at that time, they weren't sure how to handle their romance following their time at the university.

Prince William and Middleton opened up their split in 2010 during their engagement interview. The Duchess of Cambridge confessed that she wasn't happy about it.

"I think I at the time wasn't very happy about it, but actually it made me a stronger person," Middleton said. "You find out things about yourself that maybe you hadn't realised. Or I think you can get quite consumed by a relationship when you are younger."

When Middleton and Prince William split, the former decided to fly to Dublin with her mom, Carole Middleton. During their trip, they visited her first exhibition at the Urban Retreat Gallery and National Gallery of Ireland.

The media caught Middleton, but she "politely declined" to say a few words to the reporters. At that time, the media wasn't aware of her and Prince William's split.

Prince William and Middleton eventually got back and got married in 2011. They are now happily married with three kids, 5-year-old Prince George, 3-year-old Princess Charlotte, and 6-month-old Prince Louis.

Prince William and Kate Middleton
Prince William left Kate Middleton fuming after their split. Pictured: Middleton and Prince William laugh as they visit BBC Broadcasting House on Nov. 15, 2018 in London. Getty Images/Ben Stansall