How is Kenneth Branagh's Death on the Nile different to the book?

"The thing that really stuck with me about it, that was always just impressed upon me from seeing that movie at too young an age, was just this idea of murder," he explains in an exclusive interview with RadioTimes.com. "That people, nice people who you see in the shops, and on the street, who wave hello, are occasionally capable of deliberately killing one another.

"And that was a new idea for me, just this idea of murder. It's sort of like learning about death for the first time, you never go back. And then there's learning that people inflicted death on purpose – once you learn about that you can't go back. So that's really kind of a pivotal moment for me."

Of course, this new version of the story is not simply a carbon copy of the earlier film – or of Christie's original novel – and so we spoke with Green about the changes in his adaptation of the story, and why he felt they needed to be made.

How is Death on the Nile different to the book?

One of the things about adapting the work of a writer as beloved as Agatha Christie is that there are always going to be some fans who are resistant to any changes at all. Indeed, Green has encountered that directly, with his teenage niece having told him that he shouldn't change a single thing. But, insists the writer, it's imperative that each interpretation of the story brings something new to the table.

"What you want to do is to honour it, but you have to give yourself the permission to break and restructure in order to honour it," he explains. "Because whenever you adapt anything, you have to find what you love about it. And at the expense of a lot of other things you have to make sure that what you love about it comes through. And sometimes you have to undo some beautiful things in the book or some delicate things in the book, or even some interesting things in the book in order to make room for what has to happen.

"In each film, we think of it as Poirot versus something new that he hasn't really dealt with in his personal life," he adds. "In Orient Express it's Poirot versus morality, this idea that reality is not black and white, that things are complex. And it is a much more comforting notion to imagine that reality is easy black and white, but life just doesn't give you that.

"And we thought that the themes of Death on the Nile were very much about love and heat and passion, and that every character would have a chance to tell us what they feel about romance, whether it's cynical, whether it's childish, whether it's romantic with a capital R, whether it's lustful.

"And that would be a wonderful thing for Poirot to be forced to deal with because as a character he eschews romance. It's a messy, sticky, ugly thing that really doesn't fit into his neat 90-degree angled corners. So how much fun would it be for a case that forces him to really think about romance and love, and to be befuddled by it?"

One of the biggest changes in this new version is the addition of the character Bouc, who previously appeared in Murder on the Orient Express. This character does not appear at all in the original Death on the Nile, but according to Green he and Branagh were so impressed with Tom Bateman's performance in their earlier collaboration that they felt they had to write something into the script for him.

"In early conversations with Kenneth Branagh about this, he and I were just talking about what are the things that we thought went really well (in Orient Express)," he explains. "And he said, 'I love Tom Bateman as Bouc' and I said, 'I love Tom Bateman as Bouc.' He's a lovely man, and we loved his performance, and said, 'Do you think there's any way that he might return?'

"And I had been baking a subplot that I thought would be a clever adaptation of a piece of the book that we could bring through, and it suddenly clicked that that should be played by Tom Bateman. And we'd give him something really fun to do in the film, which Ken immediately absorbed and said, 'Yes, let's dive into that.'"

The other big change is that this film more thoroughly explores Poirot's past than perhaps any Christie adaptation before it, giving us an origin story not just for the Belgian detective himself, but also for his iconic moustache – which it turns out has its roots in a tragic incident in the First World War. This opportunity to delve deeper into the character was something that Green found instantly appealing.

"You know, when you have a film where you're taking Poirot as a character, you have the opportunity to learn a little bit more about him in each," he says. "It's not just only a little titbit, but how does that titbit inform this story and show some growth in it, so it's not just that Poirot in the beginning is the same as Poirot in the end.

"And we just wanted to learn a little bit of history about him. We know from the books that he'd been a policeman, and that comes through from time to time and is mentioned in the first film. But here, we also knew that just from his age and generation that he would have fought in a terrible way in a terrible war.

"We knew that that would have an effect on him and wanted to see how that might play through. Not just perhaps in the origin of the moustache, but also in the origin for his life – which is a very unique, strange, some would say a monstrous existence."

How is Death on the Nile different to the 1978 film?

Death on the Nile has previously been adapted on a few different occasions – most notably the aforementioned 1978 film – which boasted an extraordinary cast including Sir Peter Ustinov, Mia Farrow, David Niven, Dame Angela Lansbury and Dame Maggie Smith, among others.

While Green still has those strong memories of watching that version decades ago, he says he purposefully did not revisit the film until after he had written his own screenplay – in part because doing so might actually have ended up making his job a little harder.

"I have adapted things from time to time, and I wouldn't say it's a rule, but as a method I try not to look back at anything anyone's done before," he says. "For no other reason than there's a part of your writer brain that is always looking to solve a puzzle.

"How do I impart this information? How do I conflate these two scenes into one? And if you come across another clever writer's solution, your brain – through no fault of its own – will look at that and go, 'Ah, there is the solution!' And the art of adapting, the creativity of adapting is in coming into those solutions on your own.

"And it is fun to see how ideas might evolve, or to tip your hat to 'Oh, they did it better, I wish I'd thought of that.' But you have to give yourself the opportunity to personalise it, not give that little piece of my brain that's very, very lazy, a chance to go, 'Oh I'll just borrow that, no one will notice.'"

There was, however, one aspect of the 1978 version that Green was especially keen to change – the character of Salome Otterbourne, who is played in the new film by Sophie Okonedo.

"The only adaptation decision we made based on the '78 film is that I had such a strong recollection of the depiction of Salome Otterbourne by Angela Lansbury," he reveals.

"And I knew that we would have an opportunity to recreate that character as someone completely different, though still big and brash and memorable and theatrical. You don't want to out-Angela-Lansbury Angela Lansbury, so we really thought this was a chance to just bring in a slightly different personal backstory to that character, while still giving her similar roles to play in terms of the plot."

Death on the Nile is out now in UK cinemas. Visit our Movies hub for the latest news and features, or find something to watch tonight with our TV Guide.

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