When Welsh-language productions are shot, each scene is typically done twice, once in Welsh, another time in English. The reasoning is that, outside of Wales, the English-language version can attract larger, less-adventurous, subtitle-avoiding audiences. So Gwledd, a new Welsh-language eco-horror, is a rare exception in that it was shot in Welsh, and, despite reports, only in Welsh – even if it’s likely you’ll see it advertised under its more marketable English title, The Feast.

“A lot of people ask me if it was a decision to make it in Welsh,” says Lee Haven Jones, 46, the director of The Feast. “Nobody asks Scorsese if it was a decision to make it in English. I am Welsh. I speak Welsh. And this is a mode of expression for me.”

As for the film itself, The Feast is a headache to discuss without spoilers. When I meet Haven Jones and the film’s 30-year-old star, Annes Elwy, in Soho the week of its theatrical release, the first few questions immediately stumble with “um”s and “ah”s and “oh no, I can’t say that, can I?” So I promise to mention in the first three paragraphs that readers should only continue down the page once they’ve seen the film. Even acknowledging the eco-horror aspect might be too much of a reveal.

After all, for its first half, The Feast is more a slow-burn, Haneke-esque comedy of manners, its cold, precise cinematography examining a grotesquely rich, grotesquely behaved family who are holding a dinner party in a remote, mountainous corner of Wales. The hired help, Cadi, is the sole clue to the chaos that will ensue. She arrives dead-eyed, soaked to the bone, scarcely prepared to set up the big event. Depicted with an alien physicality by Elwy, Cadi is a walking question mark that grabs the viewer’s attention – just not the actual people in her presence, such is the degree of their self-absorption.

“For me, it was forgetting all the normal human habits that we have, and really looking at everything in the room like a child,” says Elwy, trying not to spoil the surprise. “Cadi looks at something, thinks about it, feels it, smells it, then looks at something else. To watch a human not abide by human rules is engaging and disconcerting.”

“I had this idea of Cadi as a tabula rosa onto which the viewer projects their own thoughts and feelings,” says Haven Jones. “Believe it or not, it’s really hard to do nothing.” He adds, turning to his collaborator, “Not that you’re doing nothing!”

With its delayed reveal, The Feast is paced like a theatrical film – a proper one made for cinemas, not a straight-to-streaming release that frontloads the opening minutes with exposition. The soundscape luxuriates in silences and what disrupts the quietude; the lavish architecture is designed for big-screen projection (or a double-page spread in a luxury magazine); and lengthy scenes unfold without dialogue, just subtle clues that Cadi is not of this Earth – or perhaps quite the reverse. Surprisingly, Haven Jones comes from a decade of TV gigs (Doctor Who, Vera), while Elwy is best-known for the BBC’s three-part Little Women miniseries from 2017.

“Television is far more literal,” says Haven Jones. “It’s like candyfloss. For me, doing this film was a process of forgetting all of that, and staying true to my instinct. Like Cadi, actually.”

“It’s a good thing it wasn’t released during COVID,” says Elwy. “With a film like this, if you scroll on your phone, you’ve missed something, but you don’t realise it because it might be a quiet thing you’ve missed.”

“The quietness is there as a provocation,” says Haven Jones. “But not everybody likes to see a provocative film.”

“You might feel like it’s slow and there’s nothing building,” says Elwy. “But you know it’s only an hour-and-a-half. That makes you on edge. You know something’s going to kick off – you just don’t know when.”

What eventually kicks off – again, it’s not too late to abandon reading this article if you haven’t watched the film – involves Cadi’s intrinsic connection to nature. More specifically, a cursed piece of land that’s been mined for profit. The loose inspiration for Roger Williams, the screenwriter, was the 14th century-written Mabinogion tale of Blodeuwedd, a woman constructed from plants by magicians. The casting of Elwy as a “Mother Nature” figure, though, alludes to young people caring more about global warming than their parents did.

“She’s more the spirit of nature than Mother Nature... My other half, he says that Cadi’s almost like Greta Thunberg gone wrong” – Haven Jones

“I would say she’s more the spirit of nature than Mother Nature,” Haven Jones posits, before adding, “My other half, he says that Cadi’s almost like Greta Thunberg gone wrong.”

Is Elwy channelling Thunberg in her performance? “Not intentionally!” she says. “Cadi’s a creature of the soil. She’s the weak one initially. She doesn’t know these surroundings. Everything’s new to her. She has to communicate with these people. She’s like a tiny, little animal. I see her way more like that than humungous Mother Nature.”

Whereas Adam McKay’s Don’t Look Up was patronising in its preachy lessons on climate change and inspired more hatred towards its creative choices than its intended targets, The Feast takes a more poetic, visual stance. During a break, Cadi lies in the forest with vines wrapped around her body (it doesn’t reach Evil Dead graphicness) and her ultimate revenge on these human specimen feels totally, well, natural.

Not the methodology, though. One particularly unnatural murder technique is so jaw-dropping, it’s presumably what earned the film an 18-rating. However, the gore occurs entirely out of the frame, the camera sticking to facial reactions. “It’s far more graphic, interestingly, to suggest something than to show it,” Haven Jones says. “The strangeness and the horror is in people’s imagination.”

After shooting The Feast, Haven Jones and Elwy teamed up again on Wolf, a six-episode BBC series (Haven Jones directed half of it, Elwy is the female lead) set to air later this year. Still, Haven Jones admits that he still enjoys reviewing reviews of The Feast. So I bring up The Hollywood Reporter’s rave – albeit a rave that praises the “novelty” and “unusual sound” of the Welsh language.

“That’s a shame,” says Haven Jones. “But when you think about it objectively, it is novel. Wales doesn’t produce many films in the Welsh language. Certainly not films released theatrically and internationally. I’d love to think this film could kick-start a movement like the Greek Weird Wave and we see a burgeoning of Welsh-language horror films.”

“Because it is, for now, an unusual, unexpected thing for people, it really suits the horror genre,” says Elwy. “It’s a whole sound you’re not used to.”

“The film is about a way of life that’s dying,” says Haven Jones. “The film is a metaphor for lots of things. There are 600,000 of us in Wales (who speak the language) and probably a million throughout the world. But it’s an endangered language, and it’s our responsibility to preserve it, breathe life into it, and make it a living, breathing, organic thing. The Feast is our way of doing that.”

The Feast is out in UK cinemas on August 19