Bill Condon is a master of surprise. The genre-jumping director always chooses unexpected projects, moving from Oscar-winning period drama Gods And Monsters and the biopic about controversial sexuality researcher Alfred Kinsey, to the musical Dreamgirls and the final two installments of the Twilight franchise. The past five years have seen him stretch himself yet again, moving from The Fifth Estate about Julian Assange to the smash hit live-action remake of Beauty And The Beast.

Given all the twists and turns in his career, it's perhaps no surprise that Condon was attracted to Nicholas Searle's 2016 novel The Good Liar, which sees a seasoned conman growing to care about a woman he has manipulated into a relationship, in order to swindle her out of her fortune. In Condon's adaptation, Ian McKellen plays conman Roy and Helen Mirren plays his victim, Betty.

Condon knew that casting two such powerhouse actors would change the tone and focus of the novel. "The novel is a psychological case study, getting into the mind of a sociopath," he explains. "But it was the character of Betty, and the back and forth between her and Roy, that seemed interesting to me. I wanted to be able to create a really dynamic two-hander for the actors."

McKellen's Roy is the consummate conman; slick, arrogant, a pathological liar, and able to act sweet and vulnerable to manipulate those around him. The director thinks that audiences find unlikeable geniuses compelling because we find their blatant ignoring of social and moral norms perversely enthralling. "I do think that's part of it," says Condon. "With other films I've done with Ian McKellen - when he played James Whale in Gods And Monsters and the cranky old Sherlock Holmes - he was always getting away with saying the most outrageous, rude things. We'd all like to say them, but won't! And the position that can put the audience in can really be delicious. Ian's character is irredeemably awful here, but still, you also enjoy that he's getting away with it."

But that idea of identifying with characters has different effects, too. "For example, we first showed Gods And Monsters at the Sundance Film Festival. There was also a screening in Salt Lake City with a very straight audience, who didn't know they were going to see a film about a gay character. And to watch an audience like that become complicit with Ian McKellen as he's trying to get Brendan Fraser to take all his clothes off, and laughing along with it, that's the power that movies have. They allow every part of our imagination to roam."

The dynamic between Roy's overtly Machiavellian scheming and Betty's enigmatic character is merely one of the intriguing aspects of The Good Liar, which addresses themes such as accountability, revisionist history, the long-term impact of division and trauma - and women reclaiming power. "Hitchcock said that suspense is the essence of cinema, but Tarantino has pointed out that revenge is the essence of at least American cinema," says Condon. "That plays out in a few ways - we even have a brief clip of Inglourious Basterds."

The director also says that the Me Too movement became an unlikely inspiration in addressing ideas of accountability and revenge. "The novel was written years ago before the Me Too movement started, so that wasn't something we wanted to glom onto, but it did become a part of the conversation. I remember when the Me Too movement started, one of the first people was Bill Cosby, and one of the repeated questions was 'Why did the women wait?'. And this isn't explicitly what the movie is about, but we did want to try and let people understand just what it takes to gather yourself after a trauma, and to face what has happened. It's a revenge story, but done in a completely controlled and ethical way."

Of course, a huge part of a director's job is working with actors, and accommodating each of their individual eccentricities and preferred acting techniques. Condon admits that McKellen and Mirren were, on paper, a tricky combination. "It is the most extreme taste of this I've experienced, of having a two-hander with two actors who have completely different approaches," says the director. "Ian loves rehearsal, loves blocking, loves working out props, will talk endlessly about a script. Helen will endure one session, but really believes that what she does is exist in the moment. I don't think it was entirely easy for them. But because they have such respect for each other, they did want to accommodate each other - she did more rehearsal, he didn't overstep, so they both got what they needed."

Looking back over his extremely varied career, Condon admits that he has a certain fondness for some films that were overlooked, such as Dreamgirls - and found some films challenging for surprising reasons. "You always read that phrase 'A director would be crazy to take that on', and I think the craziest thing I ever took on was Twilight," he suggests. "You're just jumping into something that was so culturally charged, and in many ways that was the most challenging, to make the film I envisioned when I first read it - which I mostly did, I believe."

"Then Kinsey, that film had a lot going for it, which I think was overlooked. It's a movie that came with a lot of baggage, because of a lot of right wing groups that had never given up the fight against him. The lies they told about Kinsey for 50 years continued through the release of that movie, which was frustrating to watch. But I kind of enjoyed that it made some people uncomfortable, too!"