When Zac Efron first heard about a chance to play Ted Bundy, he was wary. This was a few years before he signed on for the new film about the serial killer, and it involved a different script. “I didn’t want to jump in too early to what could have potentially been the wrong version of this movie,” he says. “I was very hesitant to go into a darker genre in what could be perceived as an effort to change my perceived image.” The script for his new film Extremely Wicked, Shockingly Evil and Vile felt, to him, like the right version: “A movie that could have been procedural and boring now explores a brand-new perspective, and is told through the eyes of Liz, the girl closest to Ted.”

It is the morning after the London premiere, and Efron is with the film’s director, Joe Berlinger, in a hotel room. He’s drinking from a large pitcher of green juice – celery, cucumber, avocado, kale, ginger, a bit of banana – and although he has a leg injury that keeps causing him to stand up and stretch, he is otherwise the picture of health.

Ted Bundy himself said that murderers don't come crawling out of the dark

Since starring in the extraordinarily successful Disney film High School Musical in 2006, Efron, 31, has been swooned over – potentially a problem as he heads further into adulthood. He has contended with some ropy material in his career, but he is an excellent actor and entertainer, and his looks mean he is often cast as leaders – the captain of the basketball team (High School Musical); the star of the dance show (Hairspray, 2007); the president of the frat house (Bad Neighbours, 2014). In many of his films, his looks are addressed head-on, as if they will only confuse the audience if no one mentions them. In Bad Neighbours, when his co-star Seth Rogen first spots him, he says: “Oh my God, look at that guy. That guy’s the sexiest guy I’ve ever seen. He looks like something a gay guy designed in a laboratory.” In the film Baywatch (2017), in which he plays a champion swimmer with an attitude problem, he is described as “an American hero with the face of a Swedish model”. In Hairspray, the lead character, Tracy Turnblad, has his picture in her locker.

‘In many of his films, his looks are addressed head on.’ Zac Efron in Bad Neighbours Photograph: Glen Wilson/AP

He is America’s teen dream, in other words, and now he is playing Bundy, one of the most violent misogynists in recorded history, who raped, murdered and sometimes decapitated women; at his 1979 trial in Florida, key evidence included a deep bite mark on a woman’s buttocks. He was convicted at that trial of two murders and three attempted murders, and later that year was given another death sentence for the killing of 12-year-old Kimberly Leach. Before his execution in 1989, he admitted to murdering 30 women, and it’s been suggested that he may have killed as many as 100.

Bundy was considered good-looking in the pantheon of serial killers – which is, of course, quite different from being good-looking in the pantheon of movie stars. It has been suggested the film glamorises Bundy, and it becomes clear Efron and Berlinger are deeply concerned about this; when I transcribe our conversation, while I don’t mention the term in my questions, they mention the words “glamorous”, “glamorised” and “glamorisation” 11 times between them.

And that is not counting what happens at the end of the interview, after I turn off my dictaphone. In seconds, the mood shifts from friendly to chilly. “Do you think it glamorises him?” asks Berlinger.

“Because I feel like you do,” says Efron. Within minutes, there are calls to say that the two men have pulled out of a scheduled photoshoot.

Berlinger, a veteran documentary- maker, whose work has led to wrongful convictions being overturned, has spent a couple of years focused on Bundy, having also made Conversations with a Killer, a four-part documentary that came out on Netflix in January, on the 30th anniversary of the murderer’s execution. It is based on more than 100 hours of death-row interviews with Bundy, as part of a project by the journalists Stephen Michaud and Hugh Aynesworth. The picture that emerges in the documentary is of a gaping void of a man, an extreme narcissist. Bundy talks on tape about the possibility of screenplay rights to his story being sold, and Michaud says that when he told him there would be a book based on their conversations, Bundy replied: “I don’t care what you say, as long as it sells.”

As Bundy’s Florida trial unfolded, he became a gruesome celebrity. In Extremely Wicked, Efron as Bundy crows at one point: “I literally just autographed my own wanted poster. I’m more popular than Disneyworld,” and that celebrity queasily persists, at a time when women he tried to murder and kidnap are still alive, as well as relatives of all the women who never came home. Speaking to New York magazine, Bundy’s former defence lawyer John Henry Browne described the US as being in the middle of a “Bundy binge” with his case discussed on countless podcasts over the past few years, and the subject of a two-hour special on the Oxygen network called Snapped Notorious: Ted Bundy. This year also brings us the documentary Theodore, by Celene Beth Calderon. Memorabilia abounded during Bundy’s lifetime, and on Etsy today you can take your pick of a huge variety of T-shirts: one features his face and the beige VW Beetle he drove, with the slogan “Ted Bundy: original Uber”; another shows his face surrounded by love hearts and the words “Ted Bundy: heartbreaker”. There are his letters for sale online, as well as mugshots, arrest warrants, a replica fingerprint chart. There is no doubt the killer would have loved the current obsession with him.

Much of Extremely Wicked takes place in the courtroom, Efron in a bow tie, playing to the crowd. Bundy, a former law student, was part of his own defence team, and Berlinger describes his Florida trial as “the big bang of our current obsession with true crime … The Florida supreme court, for the first time ever, allowed cameras in the courtroom, and for the first time ever Americans could sit at home, in the comfort of their living-room chair, and watch serial murder, serial rape, as live entertainment.”

‘Bundy is the active and central character.’ Zac Efron, Morgan Pyle and Lily Collins in Extremely Wicked, Shockingly Evil and Vile. Photograph: Brian Douglas/2018 Wicked Nevada, LLC.

The obsessive focus on Bundy has sharpened questions about who should be the focus of true crime: the perpetrator or the victims. While Extremely Wicked is framed by the story of Liz Kloepfer, a woman who had a longstanding romantic relationship with Bundy, and on whose book the film is based, the heart of the story is the killer. Kloepfer is shown only in relation to Bundy – she meets him, falls quickly in love, worries about whether he is guilty of the horrific crimes he is increasingly accused of, and turns for a while to drink. We are supposed to be drawn into her confusion and doubt, to see him through her eyes, to wonder about his behaviour – even to root for their relationship – but we can’t. We know he is Ted Bundy, and can therefore only ever pity her for being duped. Bundy, meanwhile, is the active and central character, studying for law school, travelling, planning and executing escapes from prison, defending himself in court, and manipulating first Kloepfer, and then a woman called Carole Ann Boone, with whom he fathers a child while he is on death row.

Efron spent time in the makeup chair next to the actor Terry Kinney, who plays a detective in the film, and who told him what it was like in the 1970s, he says, “to be a young person witnessing Ted Bundy’s escapades, and what turned out to be terrible behaviour. This is not a glamorisation, by the way,” he says of the film. “We tell the story purposefully without a lot of violence.” I ask if that was important to him, and he says it is. It’s absolutely true: neither Extremely Wicked nor the documentary series focuses on the details of Bundy’s violence.

The idea behind the film is to show how Bundy took the world in; how he became, repulsively, a kind of folk hero. Relatively handsome, well educated and middle class, he couldn’t possibly be a killer in many people’s eyes. He became so popular that groupies turned up at his trial (one of them declares him “dreamy” in the film). This is the argument for having Efron in the role – that he captures the charisma and image that enabled Bundy to be believed and even idolised.

“Ted Bundy himself said that murderers don’t come crawling out of the dark,” says Efron.

“Yeah, murderers don’t come out of the dark with long teeth and blood dripping off their chins, you know?” says Berlinger. “They’re your brother, your son, your lover, people you’ve worked with, people you’ve admired. What’s so fascinating about Bundy is that he defied all expectations and stereotypes of what a serial killer is. You know, we want to think a serial killer is some dark, twisted social outcast – and of course Bundy was dark and twisted – but some dark, twisted social outcast who couldn’t fit into society, because that falsely implies that they’re easily identifiable, and therefore you can avoid them. But what Bundy teaches us is just the opposite. Bundy was very well integrated into society … I think most people who were coming to that trial just couldn’t believe that he was capable of such terrible things because he was a white male in our white privileged society.”

‘How he became, repulsively, a kind of folk hero.’ Ted Bundy in court, 1979. Photograph: Ken Hawkins/Alamy Stock Photo

“Not to mention that he was a star – he was on TV and in the news,” says Efron.

I ask Berlinger about his motivation in making first the documentary, and then the scripted drama, and he says that when he first heard the Bundy tapes, he called his daughters, who are at college. He asked whether they or their friends had heard of Bundy, and they said no. “I felt for a new generation the lessons of Bundy – the social justice part – can’t be overstated. That just because somebody looks and acts a certain way, it doesn’t mean they’re worthy of your trust … There are a lot of people out there who pretend to be one thing, and aren’t, and that’s the nature of evil. Evil is not some two-dimensional monster out there – evil is three-dimensional people who are part of our society.”

Efron echoes this motivation. He says he became aware that a lot of young girls were really interested in true crime, and wondered where the fascination was coming from. “We know Jack the Ripper existed,” he says. “But never have we been in a position to look into his eyes for a moment, properly or honestly. And in this movie we get this close to what it was like to be seduced by that.”

After Conversations with a Killer came out, there was a lot of discussion on Twitter about Bundy’s looks, leading to a statement from the official Netflix account: “I’ve seen a lot of talk about Ted Bundy’s alleged hotness and would like to gently remind everyone that there are literally THOUSANDS of hot men on the service – almost all of whom are not convicted serial murderers.” I suggest to Efron that his film is unlikely to quell that discussion, and he says he hopes the film will be “a warning message. I would love, not necessarily just my fans, but anybody who watches the movie, to really invest time in who you trust yourself with, and who you think you’re safe with.”

The implication behind all this is that women could have avoided Bundy’s violence by being more careful; that they should have looked after themselves more. I ask how this would have helped in the Florida killings, in which Bundy attacked women as they slept. “He was really on a rampage for the Florida killings,” says Berlinger, “but all of his Seattle killings depended on a ruse of a fake [plaster] cast and the sincerity that he gave off, and he lured women to their deaths because he was sincere, and white, and a guy you could trust.”

I put it to Efron later on that it’s difficult as a woman to live in the world if you can’t trust anyone, particularly if, as the film shows, in that person’s personal relationships they behave lovingly. “It’s difficult as a man, too,” he says. Believe it or not, he says, one of his “character motivations” was a “psychotic” woman. “This is not a gender thing. This [story] in particular we told, but it goes completely both ways.”

“We’re not saying don’t trust anyone,” says Berlinger, “but we’re saying: eyes wide open.” He says my question about trust “implies that maybe we were glamorising it, which I do not think we are – I do not think we’re glamorising it at all”.

“We’re hyper-aware,” says Efron, “that no we’re not.”

“Because by the end of the movie Bundy is alone,” says Berlinger, “he’s had to admit to the one person he cares about the truth. We see him as needy and pathetic, about to be executed.”

“Not glamorous or standing for a cause,” says Efron. “He’s dead.”

“And really the point of the movie is to portray deception and betrayal,” says Berlinger.

“And karma,” says Efron.

As I go to leave, Efron says: “I wanted to make this film for the victims.” There is a list of all Bundy’s known victims at the end of the film, before real-life footage of the serial killer in court. There could be no true karma or comeuppance for Bundy – he was executed, yes, but only after murdering countless women who were full of potential, whose stories never had a chance to unfold, and have never been told. It is disturbing, as a culture, that we are still looking into the eyes of a killer, still in thrall to a brutal, worthless man.

Extremely Wicked, Shockingly Evil and Vile is in cinemas and on Sky Cinema on May 3