Paul McCartney was interviewed for the Sunday Times about his new children’s book Hey Grandude!, and the grandfather of eight had a shocking revelation about one of his grandchildren.

In the interview, Sir Paul, 77, tells the interviewer that one of his grandchildren — without identifying which one — was recently mugged at knifepoint.

“In London, one of my grandkids, one of my older grandkids, was mugged and got his phone taken,” says McCartney. “That takes me back to my childhood when I was mugged in Liverpool, so I am able to talk to him.”

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When sharing his experience with his granddad, McCartney’s grandson “was saying the worst thing was that he should have just thumped the guy; he came back and felt a coward. I said, ‘No, no, no, no! The guy had a knife and you don’t know, the guy might be able to use that knife.’ So it is scary these days.”

He also opens up about the similar experience he had growing up in Liverpool. “When I was a kid it was four guys and they nicked my watch. I was of a similar age. I just happened to be on my own, bigger kids came along and it was the same feeling. [I thought at the time] ‘I have got to learn karate and be a black belt — and then I’ll get ’em!’ It was the worst thing,” he admits.

Random House Books for Young Readers
Random House Books for Young Readers

Discussing how the rock icon came to become a children’s book author, he explains: “I’ve got eight grandchildren of my own. One day one of them just said, ‘Grandude, can you do this?’ and it kind of stuck — the kids started calling me that for a joke and I thought, ‘Well, it is kind of funny.’ It’s a nice old thing, so I wrote some stories about the character Grandude.”

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Now that the book is complete, McCartney’s grandchildren have given it their seal of approval. “They have read it themselves,” he adds. “They like it, I am very glad to say.”

Hey Grandude! will be released on Thursday, Sept. 5.