“Women in wild places and mental instability run right through things, don’t they?” says Kenneth Branagh, leaning forward, earnestly. “She’s very, very sensitive, and I see the ghost of her as a heroine in what she writes, in terms of keeping body and soul together, and of being an adventurer.”

He’s talking about Agatha Christie, and giving a reading of the detective novelist’s fiction that is a long way from the more traditional view of her as a comfy West Country matriarch who churned out mysteries to support her family. “I think people have been pretty tough on her,” he adds. “They’re suspicious of the volume of her output. She herself admitted that sometimes she wasn’t proud of a book when she had finished it.

“Personally I admire the prolific nature of what she does … her ability to grab the audience’s attention is really striking. The surface of what she writes has led people to dismiss her as a second-rater. But I think she is far more than that.”

Branagh is talking about Christie as he gets ready to unveil his big-screen version of her classic Murder on the Orient Express (the first cinematic interpretation since 1974), her story of a group of passengers and a dead body trapped in a luxurious train in a snow storm. He stars as the legendary Belgian detective Hercule Poirot.

“I think people often feel this about Shakespeare – they’re annoyed by his bourgeois credentials,” he says.

“He retires at the normal age, goes back to Stratford, buys houses, gets involved in disputes about rent. It feels as though there’s a sort of middle manager quality in there; he was a businessman, a shareholder, yet he wrote all these plays. That makes people suspicious.

Facebook Twitter Pinterest Prolific … Agatha Christie. Photograph: Underwood Archives/Getty Images

“With Christie, people essentially have her down as a sort of Miss Marple – a sexless, removed, bookish, woolly, very English sort of individual. And they are not aware of the intrepid, pioneering, passionate woman that she was.”

The lineaments of her life back this view. Christie had such a desire to travel – and to keep her first husband, the dashing Archie Christie, happy – that she set off on a year of travel with him in 1924, leaving her daughter Rosalind at home with her mother. She left Rosalind again when she famously vanished for 11 days after discovering Archie was having an affair; she underwent psychiatric treatment in the wake of the incident. After their divorce, she travelled alone on the Orient Express, to Istanbul and then on to Damascus and Baghdad. Her family worried about her on the trip but for her it was a way of discovering new worlds – and, coincidentally, a new companion in life since she met her second husband, Max Mallowan, on a dig in Ur. Despite her writing commitments, she worked alongside him, often in difficult conditions and exotic locations.

Branagh and I talk at Twickenham Studios. He is tired because of an exhausting schedule which is whisking him around the world, but he’s here to put the finishing touches to his film, which boasts an all-star cast: Judi Dench, Michelle Pfeiffer, Daisy Ridley, Olivia Colman, Penélope Cruz, Johnny Depp, Derek Jacobi, Sergei Polunin …

Facebook Twitter Pinterest Watch the official trailer for Murder on the Orient Express

The way the trailer is framed, with captions that reveal the type of character each star is playing, takes both the film and its director back to his youth in the 1970s and early 80s, when the posters for movies such as The Towering Inferno and indeed Sidney Lumet’s 1974 version of Murder on the Orient Express, starring Albert Finney as Poirot, were plastered across the streets of Branagh’s home town of Reading. To the boy who had moved there at the age of nine from his native Belfast, they represented a sense of possibility. “My first encounter was with their sense of glamour,” he says. “I was pretty intrigued by all the names on those posters.”

This liking for good performers coming together to make popular entertainment is perhaps what links the two contrasting sides of Branagh’s current career. There is the actor and director who is regarded as one of the best of his age; an eminent Shakespearean, the first man to film Henry V since Olivier, a talent who can gather a top-flight company of actors to perform a season in the West End which included heavy-weight productions of The Winter’s Tale and The Entertainer. Then there is the Hollywood film director, best known for the comic-book movie, Thor. And Cinderella. He grins when I point out the strange collision between Hollywood and serious stage productions.

“No one, quite frankly, is more surprised than me that I have been allowed to get away with it,” he says. “I had not anticipated or planned for suddenly finding myself in this studio groove. It is unusual, I must say. But it’s fun.”

Shot on 70mm film, his version of Murder on the Orient Express gleams as the camera dwells on the crisp table linen, the polished wood and the glistening glasses. “I wanted you to feel the snow and smell the steam – I wanted to have all the advantages of classic material and none of the disadvantages of over-familiarity,” he says.

Facebook Twitter Pinterest Judi Dench as Princess Dragomiroff and Olivia Colman as Hildegarde Schmidt. Photograph: Alamy

For Christie fans, there are some changes – to characters, to locations, to motivation – that may surprise. But all the essential ingredients are faithfully reproduced, and Branagh has added considerable depth to his portrayal of Poirot, making him more active, more passionate and more lonely. “The screenplay caught a hurt and a more tangible isolation in Poirot,” Branagh explains. “There is a kind of vulnerability about this man who appears in The Mysterious Affair at Styles with a touching gratitude to England for looking after Belgian refugees. There’s the sense of someone who has already felt the bruises of the world.”

Did he not feel any trepidation about taking on a character who has already been portrayed by 20 actors, including Orson Welles, Peter Ustinov and, on TV, David Suchet? “It’s a lot isn’t it?” says Branagh with that disarming smile. “I guess that’s where my thickish skin comes into it. You do understand that the reason so many people have played him is because he’s a fantastic character.”

There is a kind of vulnerability about Poirot, the sense of someone who has already felt the bruises of the world Kenneth Branagh

He stopped watching other incarnations when he knew he was about to deliver his own (“I wouldn’t want to get caught copying the other boys”), but recognises the various ways that the detective has burrowed into the collective consciousness. “With the amount of source material in the novels every actor is going to bring something unique and unusual, in the same way as would happen with a famous classical part. David Suchet is a fantastic Poirot, so is Finney and John Moffatt on the radio is excellent.”

Discussion about his own characterisation will, I suspect, be dominated by conversations about his moustache – grey and flourishing and twinned with a natty beard. “We probably spent about nine months on it. We started with something thinner than Charlie Chaplin’s, then something that went up, that went down. We looked at famous moustaches in movies and paintings. The luxury as an actor – and I had this before when I was playing Wallander – is that you can go back to the books and trawl for details.

“I loved Christie’s phrasing – ‘the most magnificent moustaches in England’ – and I enjoyed the fact that the risk you were taking was that you would potentially produce the impact that the moustache has on characters in the novels, who often dismiss or ridicule Poirot, or are embarrassed by him.”

Facebook Twitter Pinterest Penélope Cruz as Pilar Estravados. Photograph: Allstar/20th Century Fox

That mention of Wallander – whom Branagh portrayed in the British television adaptation of Henning Mankell’s detective books, feels significant. Christie wrote Murder on the Orient Express in 1933, on an archaeological dig at Arpachiyah in Iraq. Published the following year, it was rapturously received, though the audacity of its plot caused Raymond Chandler to remark that it was “guaranteed to knock the keenest mind for a loop. Only a half-wit could guess it.”

His damning view of the British golden age detective novel – “futzing around with timetables and bits of charred paper and who trampled the jolly old flowering arbutus under the library window” – and his preference for psychologically based novels where a “perfunctory mystery element [is] dropped in like the olive in a martini” underlines the division in the thriller market that has existed ever since.

But the dichotomy between the advocates of clever plotting and the lovers of a story that reveals a deeper truth about society or character is misleading when applied to Christie. She may write in simple sentences, but it is the way she imagines character that has ensured the longevity of her books.

Branagh, a fan of both schools of thriller, points out that there is not so much difference between them. “I enjoyed the meditative qualities of what the Wallander novels were doing. But there’s quite a moral brood in Murder on the Orient Express as well.

There is a passionate depth to Christie, even though she sometimes said her writing is merely entertainment Kenneth Branagh

“There are not only the questions of who did it, how did they do it, and why, but also the question of what now represents justice. And that issue of what justice is – when concerning crimes born out of revenge – goes quite deep in analysing whether an eye for an eye and a tooth for a tooth ultimately is a way to order civilised behaviour.”

He worked on the film at the same time as he was directing Hamlet, starring Tom Hiddleston, as a fund-raiser for Rada. “Curiously, both stories seem to me to contain the poison of deep grief, and that idea of loss and the death of innocence. I think there is a passionate depth to Christie, even though she sometimes said her writing is merely entertainment.”

Sensing that darkness beneath the surface sheen means that he has been anxious to avoid what he calls “heritage movie-making”. “I wanted to remove excessive theatricality – a sense of the sort of fluting, shrill shriek, of so called ‘larger than life’ characters. I wanted to feel that people were talking not much louder than we are now.”

Assembling his cast – consisting of old friends and colleagues and young talent – was a moment to remember.

“When they all met for the first time, they were very shy and excitable. And one of the things I was determined to do was to try to capture that energy as soon as possible. I wanted a quiver of real guilt and uncertainty when they are interviewed by Poirot, to feel as if they were people for whom the prospect of him getting it wrong and accusing them was a matter of life and death.”