Glasgow’s Krysty Wilson-Cairns on co-writing Golden Globe winner 1917: “I’ve been writing for five years and this is my first movie that has been made”

Krysty Wilson-Cairns PIC: Tolga Akmen/AFP

Krysty Wilson-Cairns is sitting in the old reading room at the top of London’s Imperial War Museum.

 “It’s not very subtle is it?” she laughs, surveying the domed, two-tier structure and the massive curved tables that follow the contours of the room.

 Indeed it’s not, but the elaborate, Dr Strangelove-esque setting is oddly appropriate. And not just because the 31-year-old Glaswegian screenwriter spent months ensconced in the reading rooms below poring over history books and front line diaries while researching the script for new war movie 1917. It’s appropriate too, because her career has blown up in a crazy way.

 The aforementioned 1917, for instance, is a pretty auspicious debut. Directed and co-written by Oscar-winner Sam Mendes and budgeted at a whopping $90m, it’s a cutting-edge war epic that looks set to be a front-runner come awards season and features supporting turns from the cream of Britain’s acting crop, among them Colin Firth, Andrew Scott, Benedict Cumberbatch and Richard Madden.

 It also had a wee royal premiere the previous evening, which Wilson-Cairns attended with her mum.

 “That was so surreal,” she says. “I’ve been writing for five years and this is my first movie that has been made. You sort of dream about what it’ll be like, but the reality was better.”

 How so? “First of all, people are liking the film, which is really rewarding. I also spent the last year and a half with Sam Mendes and the boys so it was like a little reunion.

 “And then you get to meet Prince Charles. That doesn’t happen every day. And then,” she continues, “you get all dressed up. As a writer I spend most of my life in my pyjamas, so throwing a dress on every once in a while is, you know, fancy!”

 So not a bad start to her career then?

 “Ha! Yeah, it’s probably all downhill from here.”

 That seems unlikely. Wilson-Cairns can count Edgar Wright and Avengers directors Joe and Anthony Russo among her next collaborators and she’s quick to credit Mendes and his Skyfall writer John Logan with pulling her out of the movie biz trenches where so many aspiring screenwriters’ careers languish or end.

 Her ascent has certainly been swift. Having studied at what is now the Royal Conservatoire of Scotland, she spent the year after graduation working in the BBC Comedy Unit as a “general dogsbody” before moving to London to attend the National Film and Television School. Making a living bar-tending in Soho, she wrote in her spare time and on breaks on her shifts, eventually penning a spec script called Aether, a sci-fi-themed serial killer thriller she affectionately describes as “schlocky,” but which was good enough to both land her on the 2014 Blacklist (the industry sourced survey of the year’s best un-produced screenplays) and sell to US production company FilmNation.

 That in turn put her on Hollywood’s radar, with Black Swan director Darren Aronofsky hiring her to adapt true crime novel The Good Nurse, a film that may yet happen, with Tobias Lindholm directing and Jessica Chastain and Eddie Redmayne in the leads. And then Logan, who at the time was the show-runner of Sky Atlantic’s Penny Dreadful, read Aether and hired her to write on the show’s third and final season.

 That’s also how she met Mendes. His company produced Penny Dreadful and invited her in for a general meeting. She ended up pitching him several ideas. “I don’t think he expected me to be that gallus, but I absolutely went for it. And we just hit it off.”

 Though the first two films he hired her to write fell apart, when he called her with the idea for 1917– which was inspired by a story Mendes’ soldier grandfather, Alfred Mendes, had told him as a boy – he said “third time’s a charm” and they were off.

 There was, however, one more surprise. He casually mentioned that the film – about a soldier (George Mackay) making his way across No Man’s Land to deliver an urgent message – would be shot in a simulated single take. “Then he hung up on me,” grins Wilson-Cairns. “I was like, ‘What?’ I had to text him to see if I’d heard him properly.”

 She subsequently sat at Mendes’ kitchen table hammering out ideas and figuring out the structure, then rewatched every film with notable long takes – Rope, Birdman, Victoria, Touch of Evil, Children of Men, the opening scene of Mendes’ last Bond film Spectre – before driving round Northern France to get a feel for the landscape the characters in this real-time story would be moving through. “That massively informed the writing,” she confirms. “I finished the script at the end of that trip.”

 She was also on set every day, which had the added bonus of letting her return to Glasgow when the production decamped to the dry docks at Govan early last year to shoot a crucial scene. “Believe it or not, my grandfather used to run haulage out of there,” she says. “It was so weird because I’d spent a year writing this and the production looked all over the UK for a place that would look industrial enough and French enough and they found it in my back garden. It was nuts.”

 Her Glasgow friends kept asking if they could visit the set, but she had to confess she didn’t have that kind of power. She did love the fact that local kids kept trying to break in – and especially loved the two who outfoxed security by stealing a boat and sailing across the Clyde onto the set. “It’s peak Glasgow,” she beams. “It’s like, ‘Naw, we’re getting in there.’ It was amazing.”

 Turns out she also had some of that brazenness as a teenager. Growing up in Shawlands on the Southside of the city, she talked her way onto the set of Taggart when she was 14 after spotting the Scottish TV institution shooting near her house. She went back everyday until they gave her a job, which makes her sound like the Scottish Spielberg. She laughs away the comparison, but does find stories like this fascinating. “If you don’t have any kind of personal family connection to the industry, it just seems so impenetrable, right? I just wanted to know more about it all and, luckily, people at Taggart and, later, Rebus, were very open to that.”

 It was properly life changing too: the night before she was due to go down south to study engineering at university she told her mum she wanted to do film instead. Hence why she ended up at the Conservatoire.

 And now 1917 is about to open in cinemas, followed in the autumn by Last Night in Soho, her aforementioned collaboration with Edgar Wright, whom she also met through Mendes. And after that, she’s got another three films in the pipeline that she describes as “dream projects” but can’t talk about, as well a non-superhero script for the Russo brothers, which she can’t talk about either, but does let slip is called La Hacienda.  “It’s pretty weird, isn’t it?” she surmises of her career thus far. “I think maybe one of my agents does voodoo or sold their soul. Either way they’re getting presents!”

  1917 is in cinemas from 10 January