Kenneth Branagh reveals how he brought Poirot – and his moustache – to the big screen

This glamorous tale of a tangle of strangers locked together on a fabulous night train through Eastern Europe, explodes from within, as one of the passengers is savagely murdered, while the train lies perilously trapped in snow. Danger stalks this journey and, while violence and horror reveal themselves, I found that on reading the novel its underlying emotional quality is what most haunted and moved me.

On that famous surfing safari, Christie and her then husband, Archie, left behind their young daughter, Rosalind. The longing for her absent child is powerfully present in the cascade of letters she sent home. That preciousness of family lies deep in the heart of Christie’s novel, and I found myself amazed that a book that scared and shocked me also made me cry.

Agatha Christie wrote in her autobiography, “I have sometimes been wildly, despairingly, acutely miserable, racked with sorrow; but through it all I still know that just to be alive is a grand thing.” And though I was shot through with sorrow, I was also inspired by her to make our new film of Murder a grand thing indeed.

First, the cast. Who grander from afar, or kinder up close, than Dame Judi Dench? I wanted her to play the formidable Russian aristocrat Princess Dragomiroff. Her involvement with the murder centres around a beautifully embroidered silk handkerchief, bearing the single letter H. While appearing alongside her in The Winter’s Tale at the Garrick Theatre last year, I had a similar handkerchief embroidered with the letters JD, and left it in her dressing room on top of a copy of the novel.

When I walked in a little while later, she interrupted me before I had even finished opening the door, and simply yelled: “Yes, yes, yes – I’ll see you on the platform!” She was as good as her word, and a year later on that very departure platform at Istanbul station (on this occasion magnificently re-created by production designer Jim Clay at London’s Longcross Studios), she waited patiently for her fellow passengers to arrive.

Michelle Pfeiffer came first, as the garrulous Mrs Hubbard. Penélope Cruz next, as the religious zealot Pilar Estravados, a character not in the original novel, but still with a Poirot connection in Hercule Poirot’s Christmas.

Willem Dafoe, sexy and sinister as a German professor; Daisy Ridley, warm and feisty as Miss Debenham, a woman who looked as though she – like Christie – could surf with the best of them.

And now all were there; Derek Jacobi’s butler, Olivia Colman’s maid, Josh Gad’s secretary, Leslie Odom Jr’s colonel and, right on time, Johnny Depp’s dangerous gangster Ratchett, who went down on one knee in front of Judi, kissed her hand and said: “Oh my God, where have you been all my life?”

At which point, a train whistle blew (it’s true – I blew it) and it was time to board the Orient Express. There and then, with whistles, cheers, steam and smoke, our four carriages juddered into movement as our faithfully re-created working train pulled out through the massive sound stage, and across the mile of track that we had built in the Surrey countryside.

The actors were quite genuinely astonished. So were the hundreds of crowd artists who were waving off this great symbol of the golden age of travel. There was no directing nor acting required. We merely captured the authentic delight at a glorious departure. It was both a tribute to Christie’s great evocation of the journey, and a testament to the wondrous movie magic that can be created by the great British film industry.

So many departments and skills were at work on this beautiful beginning – the final tally of jobs supported by a movie like this? Around 13,000. The visual style for the film (in cinemas from Friday 3 November) takes its inspiration from the great masters of cinema. I grew up loving the staggering widescreen landscapes of John Ford in classics like The Searchers, and the magnificent sweep of David Lean’s Lawrence of Arabia.

Recently I have been inspired by a modern masterpiece, Christopher Nolan’s Dunkirk. I had the privilege of acting in the film, and to see his use of the 70mm format to draw out the epic scope of a great story was encouragement enough to photograph my film in the same way. My previous experience of using 70mm on Hamlet had been a revelation. Now here was another subject for which this format is perfect, and which demands to be experienced on a big screen.

Haris Zambarloukos’s photography gives an almost 3D experience, with the enriched resolution offering laser detail of the setting and costumes. For a story that seeks to establish guilt in the matter of a violent crime, it provides a forensic exploration of the landscape of the human face. Neither character nor actor has anywhere to hide.

Directors and detectives have one thing in common; a desire for truth – compelling in 70mm. And talking of detectives... We must now finally consider a character as famous for his moustaches as his little grey cells: Monsieur Hercule Poirot.

When I began work with make-up designer Carol Hemming on this famous piece of face furniture, nine months ahead of filming, I had Poirot’s words in my ears, “It is an art, the growing of the moustache. I have sympathy for all who attempt it.”

Eight months and a dozen versions later, we found our own expression of what Christie referred to as its “tortured splendour”. As the exterior man began to appear, I looked for the man within, and found my key again in the words of Christie, who said she admired “his passion for the truth, his understanding of human frailty, and his kindness”.

This of course had to emerge from him in a vivid Belgian-French accent, one that dialect coach Marina Tyndall and I had to navigate while considering Poirot’s own view on the subject of his speech.

“I can speak the exact, the idiomatic English,” he said, “but to speak the broken English is an enormous asset. It leads people to despise you. Also, I boast! An Englishman says: ‘A fellow who thinks as much of himself as that, cannot be worth much,’ and so you see I put people off their guard.”

He certainly does, and never more so than in this story. Even astute Mary Debenham is fool enough to suggest that he was “the sort of little man one could never take seriously”.

No more seriously, perhaps, than an English woman pioneering the use of a surfboard at a time when others would deem it scandalous? Agatha Christie and her Belgian detective have more in common than we might suspect. After 80 years, a hundred adventures and millions of book sales, it would appear that the world has come to take them both quite seriously after all.

Murder on the Orient Express is in cinemas November 3rd