Prince William reportedly possessed a major flaw in his personality because of his former hobby.

In the book “William’s Princess: The Love Story That Will Change The Royal Family Forever,” royal author Robert Jobson said that the Duke of Cambridge’s approach to motorbikes proved just how flawed he was.

“His approach to motorbikes was a case in point. ‘Riding a motorbike’, according to William, ‘can be dangerous, but so can a lot of things really. Admittedly there are more risks involved in riding a bike than there is a lot of things… It is a risk but as long as you’ve had sufficient training you should be OK. You’ve just got be aware of what you’re doing,’” he said.

Prince William passed his motorcycle test when he was 19 years old. In 2008, he and his younger brother, Prince Harry, embarked on a charity motorcycle rally across South Africa. And according to Jobson, Prince William’s fondness for the activity caused Prince Charles to worry about his son.

“Prince Charles was torn between molly-coddling his son and opening him up to such danger by giving him his head. He believes there is no point wrapping a young man in cotton wool, but William is no ordinary young man… His determination to shrug off danger, to almost kick out at those who are inclined to restrict him, is both a flaw and an attribute,” Jobson said.

Meanwhile, Prince Charles wasn’t the only person who was worried about Prince William every time he would ride his motorcycle. The second in line to the throne’s wife, Kate Middleton, previously admitted that she also worries about her husband whenever he’s on his motorbike. In fact, Middleton previously said that she hopes Prince William would never go back to riding again.

After having three children, the Duke of Cambridge decided to temporarily quit riding his motorcycle. During an interview, he said that he needs to be more careful now that he has kids.

Prince William
Prince William attends the unveiling of The Victoria Cross Commemorative Paving Stones representing each of Birmingham's 1st World War recepients at the Hall of Memory, Centenary Square on Dec. 7, 2015 in Birmingham, England. Getty Images/Richard Stonehouse