The future king, 39, and his now-wife, 40, split for a brief period in 2007. The break in the relationship lasted around two and a half months before they reconciled at a party in Dorset.
The couple, who are currently on a royal tour of the Caribbean, are now over a decade into their marriage, and have three children together.
They have welcomed Prince George, eight, Princess Charlotte, six, and three-year-old Louis.
But the split taught the future Duchess of Cambridge a valuable lesson, she later divulged.
Speaking of the period they spent broken up, Kate described how she “wasn’t very happy” with the decision, but it helped her understand things about herself she hadn’t considered previously.
She said: “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 realised.”
She added: “I think you can get quite consumed by a relationship when you’re younger.
“I really valued that time, for me as well, although I didn’t think it at the time.”
“Kate was walking up and down and looking upset as if she was having an argument.
“But she didn’t cry. Word went round that it was William and they were having problems.
“Now it’s clear what it was all about.
“When she came back to the office she didn’t say a thing and disappeared for the rest of the day.
“We didn’t think anything about it at the time.