Josh Hartnett thinks Taylor Swift’s fans are as fanatical as the “over-the-top” concertgoers in his new film ‘Trap’.

The 46-year-old actor plays a serial killer father in M Night Shyalaman’s thriller, who takes his daughter to a huge concert by fictional pop star Lady Raven, where he is told the FBI are hunting him.

Josh told People he thought the fandom on display in the movie was exaggerated until he attended one of 34-year-old Taylor’s ‘Eras Tour’ shows in London with his daughters.

He said: “I became well-versed after the movie, but before I really didn’t know.”

Josh added about what he called the “mania” surrounding Taylor: “Some of the stuff, while we were filming (‘Trap’), I was thinking, ‘God, this is a little over the top. The amount of the fervour of the audience, and they know every word’.

“Then I went to the concert. I was like, ‘No, it’s exactly right.”

Josh has four children with his actress wife Tamsin Egerton, 35, the eldest of whom turns nine later this year.

The actor added getting ready for Taylor’s gig meant repeatedly listening to her tunes with his girls for half a year.

He said: “The thing is, my kids weren’t really into pop music so much last year when we shot (‘Trap’.)

“Then when they heard the ‘Eras Tour’ was coming because their friends at school were all into the concept, they just immediately became Swifties – and really hardcore Swifties.

“We listened to that music for six months non-stop in the car before we went to the show.

“The album that they play a lot at our house is ‘1989’, and I like that album. It’s a good album.”

Josh added his girls are also into horses, saying: “What’s fun about being a dad is that your kids introduce you to new things that you didn’t know you’d ever be interested in.

“You end up doing things that you never would do for yourself.

“Right now my kids are very into riding horses, so I’m learning about that stuff. I’m excited to learn more things (with them.)”