HANNAH Tointon was warned off watching Alfred Hitchcock’s big-screen version of Strangers on A Train when she was cast in the new production of Craig Warner’s stage adaptation of the story which arrives in Glasgow next week. Director Anthony Banks told his cast of TV-friendly faces that Warner’s script, originally seen a different production on the West End in 2013, had gone back to Patricia Highsmith’s original novel, published in 1950, a year before the film was released with a screenplay co-written by Raymond Chandler.

“Anthony told us to steer clear of the film,” says the thirty-year-old actress, probably best known for her small-screen stints in The Inbetweeners, Hollyoaks and, depending on your age, children’s shows Kerching! in the early noughties, and Switch a decade later. “I’ve read the book, which is about these two people, who when they meet talk about how they both have someone they’d like to get out of the way. One of them treats it as a joke, but the other is quite psychotic about it all. Our play is based more on the novel, and is a psychological thriller that follows the repercussions of this encounter.”

Tointon plays Anne Faulkner, the would-be second wife of Guy Haines, who, as played by Call the Midwife’s Jack Ashton, is desperate to divorce his unfaithful first spouse. A chance meeting with psychopathic playboy Charles Bruno, played by Coronation Street star Christopher Harper, on a speeding express train sees Guy become unwittingly involved in a double murder plot. While Tointon’s role may initially appear a picture of innocence, there’s more going on with Anne than is initially apparent.

“At the beginning of the play, Anne leads this really carefree existence,” says Tointon, while holed up in Brighton where the show is touring prior to its Glasgow run. “She’s from high society, and is footloose and fancy free. She and Guy are very much in love, and everything’s lovely and light. As things progress, their relationship changes, and while she obviously notices the change, she’s in the dark throughout about what’s caused it.”

If this all sounds too good to be true, there’s a light and shade to Anne which Tointon is embracing.

“It’s very different from anything I’ve done before. At first I thought, oh, it’s a play about two men, but now I think she really is the lightness in the play. It’s really nice to see her innocence in what is quite a dark piece of work, because she really doesn’t have a clue. There’s a really nice balance there, because once she does get wise to things she doesn’t shy away from it, and that’s been really good to play with. By the end of the play, she’s the one who releases Guy and sets him free, and that takes a lot of strength, so I’m really enjoying finding different ways to play that.”

Strangers on A Train will be the first time Tointon has been seen onstage since she appeared in Negative Space, playing the sister of a girl who disappeared aged eleven a decade earlier. That was back in 2009, at the New End Theatre in Hampstead. It was the year after she’d left Hollyoaks, and the year before she joined the third and final series of The Inbetweeners. Sandwiched between the two, she starred in The Children, a horror film in which two couple’s offspring turn on their parents.

“That meant a lot,” says Tointon. “It was really good to do straight after Hollyoaks, where I’d been playing this really straight girl, to do this really sparky psychological thriller. It really helped me take a look at myself. “

In The Inbetweeners, Tointon played Tara, the indie-kid romantic interest of Simon, the love-sick try-too-hard wimp who was part of the gang of geeky teenage schoolboys who drove the show.

“That was my most fun job,” says Tointon. “It was such a great group of people. It was very hard to keep a straight face a lot of the time, but I learnt a lot about comic timing.”

While Simon was roundly dumped by Tara following a catalogue of adolescent disasters, something clearly paid off beyond it, and last year Tointon and Joe Thomas, who played Simon, announced their real life engagement. The pair will be reunited onscreen again shortly in The Festival, directed by co-creator of The Inbetweeners, Iain Morris.

This is all a long way from Kerching!, the children’s comedy drama Tointon was cast in while still at school in the Essex suburb of Leigh-on-Sea. As summer jobs go, it was a bit different from what most girls of her age did.

“I never thought anything of it, to be honest,” she says. “It just felt like something I did in the summer holidays, and wasn’t a big deal, but looking back on it now it wasn’t that normal at all.”

Tointon landed the Kerching! gig on the back of appearing in a year-long West End run of Andrew Lloyd Webber and Meatloaf lyricist Jim Steinman’s musical stage version of the classic 1961 film, Whistle Down the Wind. That was when she was twelve. Other junior performers in the cast included Jessica Cornish, who would go on to become better known as Jessie J, future Sugababe Jade Ewan and Tointon’s fellow Inbetweeners star, James Buckley, who played Jay. Tointon only remembers mid-way through the conversation that she did the tour at all.

“It’s so long ago now,” she says, “that I’d forgotten I actually started out in theatre.”

Tointon isn’t being blasé when she says all this. It’s just how it happened.

“I went to an all-girls school, so in school plays we got to play all of the male parts. One of the mums was a child’s agent, and she was rounding up all the girls to go and audition, and one of them couldn’t go, so I went at the last minute and got it. It was such a fluke. I was very shy, and it really brought me out of myself. There were three teams of us, but the law about how much a child could work changed in some way, and I ended up doing it for a year, which was crazy.”

By that time, Tointon’s elder sister Kara, these days best known for stints on EastEnders and Strictly Come Dancing, was already acting.

“Acting was definitely more her thing. It was never a plan for us both to do it, but when it happened, it was lovely to have an ally to show me how it was done.”

Both ended up as regulars in Sky’s football romp, Dream Team, though once the casting directors realised how similar they looked, they made sure the siblings never shared a scene. More recently, they both appeared in Mr Selfridge, ITV’s lavish period drama about London department store founder, Harry Selfridge. For the younger sibling, there have also been roles in Penny Dreadful and The Hour.

Having dipped her toe back into theatre with Strangers on A Train, Tointon is keen to do more. As long, that is, as she doesn’t have to play it straight.

“I’d love to play Puck in A Midsummer Night’s Dream, and I’d love to do something like Bridesmaids or be in a Richard Curtis film. I’d also like to get a group of friends together, comedy people, and do something, but let it evolve quite naturally, like Best in Show or something. That would be fun.

“I don’t want to do straight stuff. I don’t think I’m the straight girl in a play. That’s not where my strengths lie. I reckon I’ll always end up doing something a bit different.”

Strangers on A Train, Theatre, Theatre Royal, Glasgow, January 22-27.

www.atgtickets.com