Zac Efron has said he was worried that taking on the role of Ted Bundy would look like a "desperate shot" at reinvention.
The 31-year-old plays the serial killer in Extremely Wicked, Shockingly Evil And Vile, a film based on the memories of Bundy's former girlfriend.
The High School Musical star admitted to being hesitant because he feared it would look like he was trying to escape his image as a teenage heart-throb.
However, he accepted the role after realising it offered a unique chance to explore the psychology of the mass murderer.
Speaking on The Graham Norton Show, Efron said: "I was very hesitant to do it, but I knew I could. I just didn't want to jump at something that could be seen as a desperate shot at trying to change my image.
"It was a unique experience and not what anyone expects. It makes me proud.
"I had a lot of reservations about playing a killer and in this genre of film.
"I wasn't interested in glorifying anything, but I was interested in the psychological aspect of whether he was capable of real love."
Bundy, who was described as handsome and charismatic, was executed in 1989 after being convicted of killing a 12-year-old and two Florida State University sorority sisters.
Before his death he confessed to killing more than 30 women in the 1970s but the true number of his victims is still unknown and could possibly be much higher.
Efron, who starred in The Greatest Showman alongside Hugh Jackman, said he hoped there would be a sequel to the hit musical film.
He said: "Hugh is working on all sorts of things including a one-man show. What's next? I don't know but I hope there is a sequel."
You can catch the full interview on The Graham Norton Show Friday, April 26 on BBC One at 10.35pm.
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