Kate Middleton, Prince William
Prince William dated Isabella Calthorpe after he split from Kate Middleton. Pictured: Middleton, Prince William attend the Men's Singles final on day thirteen of the Wimbledon Lawn Tennis Championships at All England Lawn Tennis and Croquet Club on July 15, 2018 in London, England. Getty Images/Clive Brunskill

Prince William reportedly had a crush on Isabella Calthorpe, and Kate Middleton was jealous of it.

Isabella Sullivan, a journalist for Express, Prince William and Calthorpe dated each other years ago. The socialite, who is now married to John Anstruther-Gough-Calthorpe, was dubbed as the only girl who could make Middleton jealous.

The Duke of Cambridge and the 38-year-old British heiress dated each other briefly in 2004 after Prince William and Middleton split. A year later, they were photographed together at a black-tie ball. In 2007, Katie Nicholl, a royal expert, told the Daily Mail that Calthorpe’s presence had been a constant strain on Prince William and Middleton’s relationship.

“William said he needed a break and that summer he went on a boys-only holiday to the Greek islands. Isabella was very much on the scene that summer. I would go as far as to say that William dumped Kate because he thought he had a chance with Isabella and Kate knew that,” she said.

Prince William was reportedly serious about pursuing Calthorpe, but he was rejected because she wanted to focus more on her budding career. After their split, Prince William and Middleton got back together.

Years later, Prince William and Middleton got engaged. During their first sit-down interview together, the Duchess of Cambridge said that their split helped improve their relationship.

“I think 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 are younger. I really valued that time for me as well although I didn’t think it at the time. Looking back on it,” she said (via Express).

Prince William also addressed their breakup during the same interview.

“I wouldn’t believe everything you read in the paper but in that particular instance we did split up for a bit,” he said.