According to a Mail on Sunday report from that time, Prince William called it quits because he thought the "fun" had gone from their relationship.
While Kate was left "desperately upset" as she'd believed the pair were set to marry, the Prince was spotted out partying at various London nightclubs.
Kate was said to feel humiliated by the snub, and by William's behaviour, so much so that she confronted her ex and told him he was making her look bad.
“Kate told William that he was making her look bad," one of her friends explained to the Mail on Sunday.
Thankfully it didn't take long for Prince William to come to his senses, and the couple got back together after a few months.
Speaking of their time apart in their BBC engagement interview, William said they had to “find their own way” and “grow up”, but did not disclose any further information about the reasons behind the decision.
The couple married on April 29, 2011 at Westminster Abbey at a ceremony watched by millions around the world.
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