Kate Middleton
Kate Middleton was known as Kate Middlebum in school. Pictured: Middleton greets well wishers as she attend Christmas Day Church service at Church of St Mary Magdalene on the Sandringham estate on December 25, 2018 in King's Lynn, England. Getty Images/Stephen Pond

Kate Middleton is known as one of the most prim and proper royals today. However, this wasn’t the case when she was much younger, one source has claimed.

In the documentary “Kate Middleton: Biography,” it was revealed that the Duchess of Cambridge indulged in some juvenile behavior while she was studying at Marlborough College.

Royal author Christopher Andersen claimed said that the Duchess of Cambridge had a mischievous streak in school. One of her peers, Claudia Joseph, said that Middleton reportedly once flashed her bottom at the boys out of the window.

“She was so famous for this at the school and she became known as Kate Middlebum,” Joseph said.

Meanwhile, Middleton went to Downe House before transferring to Marlborough College. While at the all-girls boarding school, Middleton was apparently bullied so her parents decided to send her to another school mid-way through the school year.

When she first arrived at Marlborough College, she appeared to have very little confidence in herself. She was described as kind of gangly, tall and awkward by her peers. But after her GCSEs, Middleton went on a trip to Argentina with the hockey team and then went on a family holiday in the Caribbean.

During the summer, Middleton started fixing her hair, and she also experimented with makeup. Upon her return to school, everyone noticed the changes in Prince William’s wife.

Despite being part of boys’ “Fit List,” Middleton reportedly didn’t have a lot of relationships when she was still a student. According to one of her friends, the Duchess of Cambridge consciously saved herself for someone special while in college.

In July 2000, she left Marlborough College and transferred to St. Andrews University. Middleton met Prince William at the institution. Prior to studying at St. Andrews University, the Duke of Cambridge first went to Eton College in Berkshire and was joined by Prince Harry in the same school years later.

Middleton and Prince William dated while they were still at the university. But they also went their separate ways briefly. In 2007, Middleton and Prince William got back together, and they got married in 2011.