The 2011 royal wedding of Kate Middleton and Prince William may have looked like a fairy tale to millions of viewers all over the globe. To Prince Harry’s longtime on-again, off-again girlfriend Chelsy Davy, however, it was a wakeup call that convinced her to end her relationship with the royal forever.

Royal biographer and historian Robert Lacey claimed that seeing Kate on her wedding day was the last straw for Chelsy, as it led her to realize that it was time for her to have a serious talk with Harry about ending their relationship.

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While Harry and Chelsy were not officially together at the time of the wedding, as they were on one of their many “breaks,” she was still invited to the wedding as someone close to the royal family. In his book “Battle of Brothers,” Lacey wrote that shortly after the wedding, Chelsy sat down with Harry to talk about Kate and about how it was time to definitively end their relationship.

“In 2011, after more comings and goings, she finally decided to go—and it was, ironically, Kate and William’s grand and glorious wedding that spring that did it for her,” Lacey wrote, according to The Mirror. “According to a friend, she told Harry that she could never make the sacrifices she had witnessed Kate making, particularly when it came to molding her life around the unremitting attention of the press.”

Chelsy later described Kate and William’s wedding as “so full on—crazy and scary and uncomfortable.”

Royal biographer Angela Levin also talked about Chelsy’s reaction to the wedding in her book, Harry: Conversations with the Prince.

“A friend revealed that seeing the enormity and pomp of the day convinced Chelsy that she and Harry had been right to separate,” she wrote. “Although they had a lot in common, she saw clearly that because they came from such different worlds it could never have worked, especially as she valued her privacy and guarded it so carefully.”

Harry would go on to find love with Meghan Markle, who he has been married to for the past two years. Meanwhile, Chelsy confirmed earlier this year to Daily Mail that she is dating a man and that she is “very happy” with him, but she is keeping the relationship private.