Twenty years ago, Mark Jenkin returned to his boyhood home in north Cornwall to shoot his debut film, Golden Burn, about the tensions between local lads and the owner of a caravan park. Jenkin had been studying in Bournemouth, then living in London and would soon move back permanently. “What’s your Cornwall?” his character asks. “Weekend getaway, summer retreat, Cornish pasties and clotted cream, pixies? Or is it your home? Not your second home – your only home?”

While he was filming in Porthcothan, Jenkin thought up another film, this one about a Cornish civil war. It was August 1999 and thousands of visitors were driving out of the county on the A30, then a single lane, after witnessing the solar eclipse. Named in tribute to Peter Watkins’s 1971 spoof documentary Punishment Park, The Holiday Park would be “like an Ealing comedy where the locals rose up against mass tourism, ending with the military carpet-bombing the whole of Cornwall, wiping it out and starting again,” Jenkin explains.

He is finally releasing a film based on that idea, having spent two decades pondering the question of who gets to belong in a county defined as much by its poverty as by tourists and second-home owners. Bait doesn’t depict civil war but existential struggle: fisherman Martin (local actor and comedian Edward Rowe) is up the proverbial creek without a boat, trying to earn crumpled £20 notes here and there by hand-netting fish and catching lobster while he saves up for a punt. He resents his brother for refashioning their late dad’s boat as a tourist tripper, and resents the posh DFLs (down from London types) who bought his harbourside cottage and redecorated it with cliched nautical tat to maximise its appeal for Airbnb. “All bloody ropes and chains. Looks like a sex dungeon,” Martin seethes, watching newcomers make a caricature out of his fading identity.

It is easy to take against haughty Tim and Sandra, with their entitlement and their fridge full of Waitrose food. But Martin is equally frustrating – stubborn to the point of martyrdom. It is quite likely that, as a fisherman, he voted for Brexit, while Tim and Sandra listen to intellectual radio broadcasts about the lies told by Vote Leave. Bait has compassion for all of them. “Everyone’s a victim to a certain extent,” says Jenkin. “They’re all trying to get by and make a living – £1 in Cornwall isn’t worth the same as £1 in London. In my eyes, the real baddie is the economic system we live in, where money is everything and you have these unrealistic aspirations.”

Bait explores the tension between tradition and progress, too. It is a blazing day in early July and Jenkin, tanned and affable in a tattered T-shirt, is drinking tea in the courtyard of Newlyn School of Art, having set a bucket of film to wash in the shade. Inside, his studio is packed with VHS tapes. Jenkin filmed Bait on a clockwork Bolex cine camera. The dense, twitchy grain of the monochrome 16mm film lends extra crackle to his story’s tension, especially given Jenkin’s love of confrontational closeups. The sound, added in the editing suite, gives the dialogue an uncanny distance and allows Jenkin to build up intimidating sonic effects – the oily chug of a boat engine, the slam of a vandalised lobster pot on the flagstones of a packed pub – the overall effect leading some critics to liken Bait to a horror film without the horror.

Jenkin’s rediscovery of physical film was part of the long journey to realising Bait. The director has been making shorts for 20 years. He directed an improvised film, Happy Christmas, in 2011. He loved making it, but hated the digital camera. “The computer was making decisions for me,” he says. “There seemed to be a little interloper in the room.” Then he had to undergo emergency surgery. During his three-week recuperation, he watched Mark Cousins’s 15-hour Story of Film documentary three times. “Hearing him being so passionate about film made me realise I’d lost the passion for it,” Jenkin explains. “I decided to retrace my steps to where I fell in love with making film – when I was 17, the first time I went to London with a roll of Super 8.”

Facebook Twitter Pinterest Isaac Woodvine and Edward Rowe as Neil and Martin in Bait. Photograph: Early Day Films

It worked: he shot 2015’s Bronco’s House, a 45-minute feature about the Cornish housing crisis, on the Bolex. It was well received, so he revived The Holiday Park idea. Jenkin explains his working methods: “We’re not transitioning into a digital age any more – we’re within it. I’m not reacting against it, but that move is something that’s prompted quite a lot of my work. It made me give up trying to keep up with it, and go backwards, technically speaking anyway, to something that will never change so I can master it.”

He acknowledges the danger of fetishising authenticity, just as he is wary of overstating parallels to his great-great-great-great-grandfather, the artist Alfred Wallis, whose primitive paintings of an already-lost shipping fleet won him approval from the St Ives school. Jenkin would rather talk about the benefits of limitations – a defining quality of Cornwall’s film scene, where, before YouTube, film-makers relied on a robust village hall screening network – and Bait’s themes.

Being from Cornwall, I found his writing as striking as the film’s aesthetic. Too often, the county is portrayed as a dopey backwater or a picturesque backdrop to Poldark’s pecs; its people easy punchlines speaking in a generic “Momerset” accent. Jenkin’s ear for local cadence is part of Bait’s spellbinding rhythm. Take this exchange between Martin and a taxi driver: “All right?” “Spot on.” “Ideal.” What probably sounds gnomic scans as a whole conversation to locals.

“Generally, it’s awful,” Jenkin says of Cornwall on screen. “I’m careful not to sound too precious about it – and it’s the same for a lot of places – but it’s a laziness on the part of film-makers. If you want a stupid character, rather than writing a complex character that’s a bit stupid, just give them a Cornish accent.” He mentions the late Cornish playwright Nick Darke, an early mentor. “If you read his plays, the way he writes phonetically, you cannot read that and not sound Cornish because he understands Cornish sentence structure. The way Cornish people speak English derives from a totally separate language where word order is different, so you get things like: ‘Going down the shops, are ya?’”

Facebook Twitter Pinterest Mary Woodvine and Simon Shepherd as Tim and Sandra in Bait. Photograph: © Early Day Films Limited

He admits he could be criticised for writing the uptight “upcountry people” simplistically. “I could always say: ‘Well, I’m just redressing the balance a little bit.’” He laughs. The important thing, he says, is that local fishermen feel understood. Bait isn’t set in Newlyn – its location is imagined, never named – but it is inspired by Jenkin’s home. Fishing is “the heart of Newlyn”, he says. “Without it, we would be another gentrified part of Cornwall.”

Facebook Twitter Pinterest ‘Newlyn fishermen deserve better’: an anonymous protest in Newlyn. Photograph: Laura Snapes/The Guardian

Down the hill in the village, someone has attached a handwritten sign to a lamp-post: “Newlyn fishermen deserve better.” The sentiment is vague, but palpably desperate. In 2016, Newlyn was the largest fishing port in England for landings, but it is among the 25 of Britain’s 41 ports classified as deprived. In May, a report outlined the mental illness crisis in Cornwall’s fishing community, stemming from poor work-life balance, precarious employment and weather, dangerous working conditions and sleep deprivation.

“They’re the last hunters, and they’re my heroes,” says Jenkin. “I’d really love them to see it and for them to know that there is somebody who’s putting the complexity of their lives on screen rather than being treated simplistically as a political bargaining chip. They’re always demonised, whether it’s politically or environmentally.”

The EU referendum took place about a year before Bait started shooting, but the result didn’t change Jenkin’s story. “You could see it coming,” he says. “It’s a disenfranchised people who were given the chance to reject something. Fishermen are always getting screwed over.” Still, he doesn’t think Brexit is the answer. “A complete rethink in how you treat working people and industry is actually what’s needed. The fishermen will get screwed over again.”

He has not seen the cloying film Fisherman’s Friends, Bait’s polar opposite. “So I couldn’t possibly comment.” He laughs.

Facebook Twitter Pinterest Jenkin pictured at Newlyn harbour. Photograph: Peter Flude/The Guardian

Bait’s local premiere takes place at Newlyn Filmhouse, an arthouse cinema in a former fish merchant that opened in April 2016. It is a brilliant local resource, but doesn’t it exemplify the tensions in Jenkin’s film? “There’s a danger that Newlyn will get gentrified like a lot of other places,” he admits. The old warehouse “could have easily been holiday flats. It is a funny one – I’m opposed to gentrification, but if it’s an arthouse cinema, we’ll let it go.”

That is not as much of a cop-out as it sounds: “The thing is, with Newlyn, historically, there’s always been a link between the arts world and the world of fishing,” says Jenkin. “They’re not that different, really.”

He brings up the prewar slum clearances, when Penzance town council intended to replace 350 “squalid” Newlyn houses with a new estate. Artists including Stanhope Forbes and Geoffrey Garnier joined local fishing families in challenging the plans. Together, they managed to save more than a third of the homes. It comes back to the idea that Jenkin has spent two decades refining: rural communities can’t afford to be stagnant. They have to evolve, but the line between survival and exploitation is a fine one.

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The characters in Bait eventually find a balance, neither retrenching in old ways nor selling out. More than clotted cream and pasties, perhaps that resourcefulness is the true nature of Cornish identity. “Historically, there was no road heading east out of Cornwall, but they had all these sea routes to the rest of the world, trading, alliances,” says Jenkin. “I see Cornwall as an outward-looking place.”

Bait is out on 30 August. Click here more information on Q&As with Jenkin.