Saul Dibb is a London native whose films have included The Duchess, about British royalty; NW, an adaptation of Zadie Smith’s novel about contemporary Britain; and now Journey’s End, a drama about British soldiers during World War 1. However, Dibb’s love of film has its roots in Ireland. The son of documentary maker Mike Dibb, the actor reveals that, “My Mum met my Dad in Dublin, they were at Trinity College, and that’s where my Dad discovered a love for film, going to see Jean-Luc Godard films in about 1959. I was obviously intrigued enough by his passion to become interested in film then.”

Dibb’s wife is also a documentary filmmaker, currently working on a piece about a paediatric intensive care unit. He does ask his parents and wife for notes on his work, “but only during the process – when it’s done and dusted, you don’t want any notes other than ‘It’s great!’”

Luckily, they have all signed off on Journey’s End, a beautiful adaptation of RC Sheriff’s 1928 story about soldiers during World War I. Starring Sam Claflin, Asa Butterfield, Paul Bettany and Toby Jones, the film follows a small group of soldiers who are on a six day rotation at the front, when they receive word that an attack is imminent. Rather than panic, the soldiers demonstrate a stiff upper lip and try to mask their fear and dread. The film becomes a fascinating psychological portrait, which is what attracted Dibb to the project.

“It felt like a really honest, very darkly funny exploration of experiencing war,” he says. “It’s blackly funny, in that they don’t want to talk about the elephant in the room. It seemed like a chance to make a film that was powerful and unsentimental, about a war that I kind of knew, although not in the way that it was written. I liked the idea of focusing on this small group of men in this pressure cooker situation and getting to know them over a few days.”

There are some very powerful scenes in the trenches, with the solders singing the bleak refrain of, “We here because we’re here because we’re here…”

“Yes, the nihilism of it,” nods Dibb. “That line ‘We’re here because we’re here’ – it’s not because there’s a point, it’s just because we’re here. But the stiff upper lip thing – it’s become a stereotype over time, but I think it’s slightly misunderstood in some ways. Because you might see that in the film, it’s often people putting on a brave face to save other people, to protect other people’s emotions. So when you see Osbourne chatting to people or walking – it would be much easier for him to just cry in a corner.

“But he’s doing it in an altruistic way, to save Raleigh. We tend to think of the stiff upper lip in a very derogatory way, but I think there’s a tenderness to it, it’s empathetic. For me, one of the most powerful scenes is when Paul Bettany’s character talks to Asa Butterfield’s character before they go up to the raid, precisely because they’re not talking about it. We know what’s going to happen, but this officer is working so hard not to let this young man think about it.” Though Journey’s End is a classic British story that has been adapted for stage and screen before, Dibb felt that this new version would feel relevant today.

“I remember I got the script right after the Brexit vote,” he recalls. “I felt we were entering a new phase politically, and there was something to the idea that we were going to break our ties with friends and allies. You just knew the narrative was going to tap into people’s underlying prejudices against people who were French or German, and all these things that happened. I feel it’s dangerous and reckless, and so I think for me and the writer, Journey’s End felt relevant. It’s that issue of how you play with peace.”

This isn’t the first time a period film of Dibb’s has been marketed for its prescience. For the release of The Duchess (a Keira Knightley-starring drama about the 18th century aristocrat Georgie Cavendish), the marketing heavily referenced Princess Diana – a cynical move that Dibb wasn’t too fond of.

“Yeah, none of the people involved in the making of the film were happy with that!” he laughs. “I understand why they did it, they spent a lot of money on the film and let us make the film we wanted to make – but it was marketing. It’s a pretty Route One way of reaching an audience. One weird line in the trailer was ‘History is repeating itself’, which was just wrong!”

But in the course of his career, marketing has really been the least of Dibb’s challenges. While working on the 2015 film Suite Franciase, starring Michelle Williams, Harvey Weinstein was the film’s producer. Dibb said Weinstein pulled the film in a creatively different direction, and was “bullying” in the process.

“My differences were obviously different than a woman’s,” says the actor, “different to sexual assault. But these experiences affect people in profound ways. I was lucky enough to carry on making films and to come back from that, but it has deeply affected some women, both personally and professionally. With Suite Francaise, we fought very hard to make the film we wanted to make, but it was made very difficult for us.” Dibb says he became “increasingly” aware of the rumours about Weinstein’s harassment of women at that time, but like many, felt powerless in the face of such a dominating force.

“It’s difficult,” he sighs, obviously disturbed by the recent revelations. “I talked to people about it, saying, ‘How is this happening, we need to stop this.’ Journalists too, because it was no secret. It was also no secret that people were saying ‘He’s too powerful to stop.’ How do you stand up and talk about allegations that you haven’t heard first hand, to someone’s who is incredibly litigious, and will threaten to destroy your career? It makes it very, very difficult. So there were lots of people with good intentions who would have loved to have done that, who weren’t able to do anything.”

Dibb does express gratitude to the women who came forward about being abused, and notes that it has marked a huge shift – and not just within Hollywood.

“Society has listened, hasn’t it?” he remarks. “Because it’s not an industry thing, it’s a power thing. It’s about men with power and how they abuse it. But absolutely, it’s not about these absurd conversations like ‘Oh, now how can a man ask a woman on a date, or can a man touch her knee?’ That’s absurd. This is about men who have abused power in these pyramid-like hierarchical structures, where some individuals can be hugely powerful. Hopefully that can change.”

Journey’s End is in cinemas from February 2.