Bruno Dumont is famed for making relentlessly grim films that show the savage side of humanity. So why has he shot a knockabout comedy about a buffoonish cop? The French director explains how P’tit Quinquin came about – and why he has no regrets about casting a gardener who refused to learn his lines

I’m a little apprehensive about telling Bruno Dumont how funny I found his new film P’tit Quinquin. I half-expect him to bristle like Joe Pesci in GoodFellas: “Funny how? You think I’m here to amuse you?” After all, the French writer-director is legendary for the severity of his films and of his own sometimes taciturn manner. His work – from his 1997 debut La Vie de Jésus to the harrowing artist biopic Camille Claudel 1915 – characteristically portrays the bleaker corners of the human condition in a filmic language that can be dauntingly austere. The idea of Dumont turning joker seems as plausible as Béla Tarr signing up to direct the next Fast and Furious.

And yet, not only has Dumont made a comedy, it’s also genuinely funny and surprisingly knockabout – while still unmistakably the work of an artist who habitually mines his own northern French background for images of humanity’s savage side. P’tit Quinquin – the name of the film’s pre-teen protagonist and of a local Picard lullaby – is a comedy thriller about two bumbling gendarmes investigating a grisly murder. As bodies pile up along the Côte d’Opale, we’re treated to pratfalls, malapropisms, bizarre cattle mutilations and outbreaks of corpsing by a cast who seem to be having a rare old time. Released in Britain as a 200-minute feature, P’tit Quinquin was made as a mini-series for French TV, attracting 1.6 million viewers – an unprecedented audience for this most intransigent arthouse auteur.

So why did Dumont turn to comedy? “My producer kept asking me, ‘Are you sure you don’t want to do something for television?’ I really didn’t – I don’t much like television. Finally, I came up with a fairly outlandish proposal, by way of provocation. I never thought they’d go for it.”

Facebook Twitter Pinterest Bruno Dumont. Photograph: Matt Carr/Getty Images

Born in Bailleul, near Lille, the former philosophy teacher has usually chosen to make films about his own region and its people. He’s famous for casting non-professionals, whose variously raw or awkward screen presences have led to accusations that Dumont is contemptuous towards his working-class characters and those who play them. But he likes to use people who are out of work, he says, because bosses are rarely willing to let employees go off on extended film shoots: “My actors get to work for three months, they get paid, and it all works out well.”

Dumont’s policy is above all about capturing people that don’t usually survive the normalising filter of the casting process. “Cinema usually recruits people who are exceptionally beautiful – I like putting very ordinary people in the spotlight. Walk down any street, you’ll see plenty of people who are pretty singular looking. People think that the kid who plays Quinquin [12-year-old Alane Delhaye] “looks weird, but he doesn’t. Look around you, there are loads of kids like him.”

But the casting question is especially thorny when Dumont works with people who are disabled or who have learning difficulties, as in P’tit Quinquin. He has been accused of objectifying such people or setting them up for ridicule, but the problem, he insists, is not his but the viewer’s. “I have a clear conscience. Some people think I’m laughing at my actors. Others say, ‘You must love those people a lot.’ You have to decide whether or not you’re looking at something that disturbs you. It’s impossible to work with people you don’t respect. The people I work with are actors, and I have their confidence. If I didn’t, they wouldn’t be there.”

P’tit Quinquin certainly breaks the usual decorum barrier around screen disability – particularly in the comic scene in which a young man with learning difficulties joyously wreaks havoc in a restaurant, or in the running gag involving Quinquin’s Uncle Dany, who keeps swiveling round in circles before falling flat on his face. “They’re acting,” says Dumont of his performers. “We spent a lot of time rehearsing, and it’s actor’s work.”

The reason why Bernard keeps moving his head about is because he's listening to me feed him lines via an earpiece Bruno Dumont

Jason Cirot, who plays Dany, came up with the falling-over routine: “He said, ‘Let’s put this in, it’s something I love doing.’ He really worked on the timing of his falls.”

The real star of P’tit Quinquin – playing a sleuth more clueless than Clouseau, more crumpled than Columbo – is Bernard Pruvost. A bushy-browed man in his late 50s, Pruvost is in real life a gardener at a workshop for people with disabilities. With his heavy Pas de Calais accent and his ceaseless facial tics, he’s a mesmerising and winningly jovial presence. In fact, says Dumont, Pruvost’s twitches are more pronounced on screen than they usually are. “I think his nervousness brought that on. It was also exacerbated by the fact, after two weeks’ shooting, he decided he’d had enough of learning his lines, so I had to give him an earpiece. The reason he keeps moving his head is because he’s listening to what I’m saying in his ear.”

Behind all the buffoonery, P’tit Quinquin offers an unsparingly grim view of its characters and their world. Young Quinquin and his trumpet-playing sweetheart Eve are forever sharing devoted hugs and being admired by adults as paragons of childish innocence. Yet Quinquin is also a racist bully who persecutes two immigrant boys. Dumont sees no contradiction in showing his hero as both an adorable scamp and the embodiment of the worst aspects of French society.

“That’s the power of humanity,” Dumont says. “An extraordinary capacity for love, and an extraordinary force of aggression. Children are the same. That’s the sort of thing that worries the civilised viewer, who would prefer those things to be separated out. People want a character to be all good or all bad, not both – but that’s what the truth is.”

P’tit Quinquin is not the first Dumont film to address France’s racial and cultural tensions. Hadewijch, from 2009, was about a novice nun who finds common cause with radical Islamists. It was a critique of fundamentalism, both Islamic and Christian, from a director who is often viewed as one of cinema’s genuine mystics, but who forthrightly rejects religion as such. “For me, the religious is something that hardens the soul. We need spirituality and we can find it in art, but not in religion, which simply obscures things and makes people superstitious. I can’t believe we’re not already done with all that.”

Facebook Twitter Pinterest Alane Delhaye, left, as Quinquin. Photograph: PR

Dumont has always been associated with the more confrontational edge of European cinema. But these days, he says: “I’m more interested in comic films than in provocation – that doesn’t interest me any more.” His next film will be another comedy, entitled Ma Loute: “It’s very broad, very eccentric, and I’ll be pushing it a lot farther than P’tit Quinquin.” Again set on the Côte d’Opale, the film is another mock thriller, this time taking in a love story – and a touch of cannibalism.

It will also mix Dumont’s customary unknowns with some major French names – Valeria Bruni Tedeschi, Fabrice Luchini and Juliette Binoche, the first star Dumont ever worked with, and who gave her finest performance in years as the sculptor heroine of his Camille Claudel 1915.

“I want to push Juliette as far into comedy as Camille Claudel did in the direction of darkness and tragedy,” Dumont says, referring to one of the most emotionally pitiless films of recent French cinema. “Mind you, that had its laughs, too.” After that, he’s planning a film about Joan of Arc. Whether it too will be a rib-tickle remains unclear, but it will have tunes – it’s going to be Dumont’s first musical.

Judging from Dumont’s deep, measured voice over the phone, it doesn’t seem as though he’s suddenly turned into a James Corden-like figure of riotous fun. But he does seem more relaxed than in the days of his early features, when his sardonic reserve could freeze a festival Q&A audience at 10 paces. So could it be that with P’tit Quinquin, he’s sending up his own hyper-solemn image?

“I’m definitely not afraid to parody myself,” he says. “Especially since, in serious cinema, there’s that tendency to surround things with a certain mysterious aura. Film-makers tend to pontificate, to adopt a rather grave, lofty persona. I’m not like that at all.”

• P’tit Quinquin is released on 10 July.