1917 is a unique war movie as it's told entirely in real time and edited as though it's one continuous two-hour shot.
Unsurprisingly, that approach had its fair share of challenges.
Or, as co-writer Krysty Wilson-Cairns put it to Digital Spy: "Everything's different. Annoyingly, everything's different. I could talk for hours about how everything's different. I could start bringing in bits of script and be like, 'Gaze upon this hard work'."
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However, she decided to just break it down into two major things, the first being how often does a two-hour block of your life reflect a movie?
"Does it have a beginning, middle and an end? Satisfying character arcs? A couple of action set-pieces? Does it have anything that's worth making a $90 million movie on? And I think that's true for probably everyone. It was definitely true for me," Wilson-Cairns noted.
"So as a writer, what you have to do is, you have to sit down, and you have to go, 'How far can I push reality? Where are the edges where this story, which has to feel believable and has to feel real, where are the edges where it stops feeling real?'."
The second, equally as challenging, point was "telling the story as one shot" which changes the script completely.
"With this, you had to completely retrain your brain and somehow tell a story in which everything unravels like a ribbon, so that it's all connected, and it all feels like the same part of the same tapestry," she continued.
Related: Is 1917 based on a true story?
"So, literally, frame by frame, you have to describe the shot and the scene. But you can't do it in a technical language, because it has to be engaging to the reader.
"And then also, emotionally, you have to have all the dialogue. Everything has to satisfy. So it has all the pitfalls and the problems of a normal script, just with extra levels of pain."
The one bonus of working on a movie that had to be so meticulously crafted down to the finest detail was that Wilson-Cairns was on set throughout filming, ready and waiting to rewrite any scene that didn't quite work.
Fortunately, there wasn't anything too major that needed to be changed.
"It was always very small stuff. To be honest with you, it was rehearsed to within an inch of its life, because actually, technically, it was only achievable if everyone knew what they were doing," Wilson-Cairns said.
"I think the main things that happened on set that required rewrites were: sometimes the actors were so good, they didn't need words. I was advocating — I was like, 'Cut that line, cut that line, cut that line'.
"Kill your darlings, because those darlings are much prettier. Let them be darlings. So, yeah, there was a lot to do on set for me."
Wilson-Cairns also spoke to Digital Spy about the casting of Benedict Cumberbatch and Andrew Scott, as well as the unexpected nod to Fleabag's Hot Priest.
1917 is out now in the US and is released in UK cinemas on January 10.
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Movies Editor, Digital Spy Ian has more than 10 years of movies journalism experience as a writer and editor. Starting out as an intern at trade bible Screen International, he was promoted to report and analyse UK box-office results, as well as carving his own niche with horror movies, attending genre festivals around the world. After moving to Digital Spy, initially as a TV writer, he was nominated for New Digital Talent of the Year at the PPA Digital Awards. He became Movies Editor in 2019, in which role he has interviewed 100s of stars, including Chris Hemsworth, Florence Pugh, Keanu Reeves, Idris Elba and Olivia Colman, become a human encyclopedia for Marvel and appeared as an expert guest on BBC News and on-stage at MCM Comic-Con. Where he can, he continues to push his horror agenda – whether his editor likes it or not.
