Based on Ian McEwan’s Booker Prize-nominated novel, On Chesil Beach is a moving work of regret and longing starring Saoirse Ronan and Billy Howle as a young married couple in 1962 whose wedding night uncertainty has sad repercussions that affect the rest of their lives.

Working with McEwan himself, who wrote the screenplay, it marks Dominic Cooke’s first feature film following a wealth of theatre experience – as writer-director on a host of award-winning plays, and including a seven-year stint as artistic director at the Royal Court Theatre.

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With On Chesil Beach now in cinemas, following its UK premiere at the BFI London Film Festival, we sat down with Cooke to discuss the adaptation, its message and taking the leap between theatre and film.

The novel is fairly light on dialogue but your film is full of it. How did you ensure your film remained truthful to the book?

I suppose I was going the opposite way – not to betray the book, but to make sure that we were really thinking about the movie. When I first came on board there was already a draft so he’d already made some choices about the structure. But I was always, especially in the last act of the film, thinking about the difference between the experience of watching a movie – what an audience needs and expects from it – and reading a novella.

On Chesil Beach (2017)

What was the biggest challenge within that?

The end, because the end of the novel is very open and I think that’s OK with a novel. For us, we needed to do something that was more cathartic that gave the film a climax. So that’s what we spent a lot of time thinking about, and how you do that while staying true to the story and the essence of what this piece is about. It’s amazing how the slightest change in what we revealed made a massive difference to the emotional impact of it.

It’s your debut film, though you’ve got extensive theatre experience. What was the biggest challenge in making that leap?

It wasn’t about the technical side of filmmaking. It was about dealing with the business side of it and the executives, because the great thing about working with theatre is it’s very pure. It’s you and a bunch of actors and a writer in a room: you make something, you show it to an audience, you stop changing it. Because there’s more money involved, film is a much, much more collaborative process, and nowadays films are made not by one producer but by many, many producers.

So you have to learn how to manage creatively all the input you’re getting, and to make sure the film’s not then diluted down into something that pleases everyone, but that it’s true to you.

On Chesil Beach (2017)

In 2015 you told The Stage that “Running theatres is becoming a job that almost can’t be done.” Is there anything about filmmaking that would make you say that?

My guess is that it’s very, very hard now for auteur directors to emerge because the system mitigates against it. If you look back, even the small scale people like Mike Leigh or Ken Loach, or in the States people like – he’s not a name that people want to conjure up at the moment – but early Woody Allen movies. These are very authored movies, and in those days you had basically one producer and one director and the money came from one place, and that allows a voice to emerge, an individual voice.

You see this a bit on television actually, because writers and directors are empowered to author something and it produces great results. But in film what’s happened is there’s multi-strand financing, and in order to get the money out of people they are promised a creative role on the film.

On Chesil Beach (2017)

It’s not that anyone’s planning to dilute the work. It happens almost accidentally, but in order for everyone to agree on what’s right it has a very conservative effect on films. The result is that in terms of emerging directors, it’s much harder to make films that have a very strong, authorial voice without making very big compromises or having to just do it on a tiny budget, because that’s the payoff. I think that’s a real problem now in the movie business, and it’s a shame.

What advice would you give the lead characters?

My advice would be don’t worry about having sex tonight. It doesn’t matter if you don’t and don’t worry if you feel frightened. Just allow each other space, because I think the tragedy of the story is that if he hadn’t come charging down the beach after her, they might have had a different kind of conversation a couple of hours later. What Ian McEwan said was, “The message of the film was really they should have just had a cuddle.” And he was right. I think that now there are huge pressures on young people, partly because of the internet and social media. But I think we at least have an ability – or a cultural currency – to talk about feelings.

Does the film have a message?

I think partly the message that has evolved is let’s not go back. If you think about Trump and Brexit, both of which happened while we were making this film, and that, kind of, toxic nostalgia for this idea of the past where everyone was white and everything was perfect.

Of course that wasn’t the case and, actually, I think it’s a very dangerous thing to imagine that we can ever go back. I think there’s a real truth to this because these two people aren’t particularly materially badly off. I mean he’s from a lower-middle-class background, she’s from a more upper-middle-class background, but they’re not starving. And yet they are emotionally unbelievably repressed and damaged, so I think in a way that’s the message of the film in the present climate. Let’s move forward.