While working on the mockumentary The Moment, Jamie Demetriou filmed a scene in which his character, Tim, is trying to have an important conversation with Charli xcx in a vehicle. The problem is, his seatbelt is stuck, and he’s sitting in front of the singer. No matter how he contorts his body, he is physically unable to make eye contact. He wrestles with the thing, gains a few inches, then is snapped back upright — much to his character’s annoyance and the audience’s delight.

This wasn’t in the script. Rather, it’s a classic Demetriou addition, the kind that has earned him cult status in Britain (and a couple of BAFTA Awards): slapstick comedy combined with an almost poignant knowledge of the character he’s playing. 

Demetriou, 38, is best known for Stath Lets Flats, the sitcom he created, wrote, and starred in for three years, about an incompetent young man desperate to take over his father’s struggling realtor’s business. Standing at 6’3” and blessed with a particularly expressive face, Demetriou would map out scenes with physical comedy in mind, pushing a table just far enough away from a couch that he struggled to reach his coffee. (Cue awkward scrambling.) For driving scenes in The Moment — out January 30 in the US and February 20 in the UK — Demetriou couldn’t resist some similar plotting. “I remember clambering around my friend’s car trying to think about positioning,” he says when we meet in London in December. “Because when you find that one thing to be doing, that is where heaven resides.”

American audiences might recognize Demetriou a little better from his turn as Fleabag’s Bus Rodent, or cameos in Barbie and Jay Kelly, but The Moment’s casting team wanted him specifically because of his work on Stath. “He represents the next generation of really classic British comedy,” the film’s co-writer Bertie Brandes says. “And we wanted the film to have a tonally British sense of humor, even though we were always going to have a lot of American actors.” (Among others, the film stars Rachel Sennott, Kylie Jenner, and Rosanna Arquette.) “So it felt extremely exciting for us to drop him into an unexpected world, with characters he wouldn’t have encountered in things he’s done so far.” 

That, it turns out, was exactly what Demetriou was looking for. After a decade playing extroverted walk-on parts in comedies, at the start of last year he was feeling fatigued. “I’d been sent stuff for a while that I just didn’t feel was right,” he says. “It felt like one big face after another. If I’m going to grow as an actor, I need to show that this big face doesn’t always have to be wobbling all over the place.”

Demetriou already knew Charli a little from the London scene, but he still had to audition. After landing the role, but before filming started, he took himself on a retreat to the English coast, hoping to make headway on his own writing projects. There, he had a call with Charli, Brandes, and the film’s director, Aidan Zamiri, to better understand his character. Tim is Charli’s long-suffering manager — the person who is “actually the closest person to her and kind of bears the brunt of her emotional turmoil,” Brandes says.

Through sheer coincidence, I was in the room for this exchange, reporting a story on Zamiri. On the call, Demetriou was an excited, humble listener, but by the end he was bubbling over with creative ideas. Zamiri remembers it being an early confidence boost that the project would work out. “I felt so emboldened by his excitement,” the director says. “And honestly, as soon as we knew he was involved, we were rewriting drafts with him in mind. His presence helped us see how the role could be bigger.”

Filming took place around London last spring, and the cast partied together between shoots. (Demetriou even ended up at Charli’s Italy wedding in September.) Demetriou swallowed his pride when, occasionally, he’d arrive on set wearing his own clothes, not thinking they’d be relevant to a character who’s canonically uncool, only to be told that he looked “perfect” for that day’s scenes. “I had to accept that that’s who I am in the context of this gang,” he jokes. 

Still, being around the artist and members of Charli’s creative team, many of whom have known her since high school, was a reminder of the kind of environment he craves. “The best I can hope for is that I’m working with people who are totally in touch with their own sensibilities, because I struggle to be in touch with mine,” he admits. “These past few years, I’ve been falling down the cracks between my sensibility and what I believe is expected of me, and that’s caused me to get a bit lost. So I was excited to be infected by the confident connection Aidan and Charli have. I want that to rub off on me.” 

Happily, the benefits went both ways. “He really created the character,” Brandes says. “We had written it, but he gave us the person. We were blown away when we got into the edit because there was such depth there, and new things in every take. It was like watching a way better film than I thought we’d written.” Zamiri is similarly appreciative. “There are certain scenes where we’re seeing Charli’s emotions, but we’re interpreting them through Jamie’s performance,” he says. “That’s the kind of thing we wouldn’t have figured out on the page and didn’t build a plan for, but he just had it.” 

Demetriou was delighted to see the final cut in January. The film, which merges the workplace comedy beats of The Office with the cool of a Sofia Coppola movie and the manic energy of a Safdie project, felt to him like “genre invention, which is needed in a time where it feels possible that film might not just go backward, but stop.”

Meanwhile Demetriou, who recently became a father, has been taking some time to land on what his own next creation should be. An idea is taking shape — something to do with “people trying to have incredibly deep conversations,” he says. “Pushing chats to their absolute limits.” But he’s still in refinement mode. Stath, after all, took a decade: five years to pitch, five to make. Although the industry seems eager to greenlight his projects — an anticipation that’s bound to increase after he appears as Mr. Collins in Netflix’s upcoming Pride and Prejudice adaptation — Demetriou only wants to make “something that should be made. It’s so easy to just go, ‘Okay, uhh, it’s about a truck driver who’s so damn tired, and that’s where the jokes come from,’” he says. “But then suddenly I’d be on a set in this truck with a fake beard on, and my girlfriend [is] going: ‘Do you actually like this? Or are you just … doing it?’” 

Still, one gets the sense that character inspiration is never far for Demetriou. Thanks to some logistical reshuffling, our interview took place in an older woman’s office at a photography studio. The woman, after kindly letting us use her space at the last minute, chose to remain at her desk for the duration. I was seated facing away from her, but Demetriou had a clear view. After she left, I mentioned the odd set-up, and he told me that throughout our conversation he’d been distracted by her making “deep nods to certain points that I made, but mostly to points that I don’t think were profound in any way.” 

“There was one thing I said that was like, ‘Yeah I’m thinking of working on some new stuff,’ and that got a big nod.” He laughed. “It was like she was saying, ‘Yes, that’s the thing!’”