Ken Loach: Why Britain’s only hope at Cannes is really an optimist

From 16 May, when the Cannes Film Festival opens, the Italian director Nanni Moretti and his jury will settle down to watch 21 films competing for the Palme d'Or, the European film world's highest prize. Among the contenders are David Cronenberg's Cosmopolis, Michael Haneke's Love, Walter Salles's On the Road, the veteran Alain Resnais's You Ain't Seen Nothing and John Hillcoat's Lawless. One Canadian, one Austrian, one Brazilian, one Frenchman and one Australian. Are any British films in the running? Just one. It's called The Angels' Share, and it's directed by Ken Loach.

Thank God for Loach. Without him, modern British cinema would lack almost all intellectual credibility abroad. Without him and Mike Leigh, British cinema could boast no auteurs worthy of the name. Both men have won the Palme d'Or – Leigh with Secrets and Lies in 1996, Loach with his brilliant portrayal of the Irish Civil War, The Wind That Shakes the Barley, in 2006 – but the latter has had had no fewer than 11 nominations since 1990. Without him, the French could write off British film as a lightweight hybrid of charm and nostalgia, rather than a medium for political seriousness and questing for truth.

Without the French, contrariwise, Loach's films might have died of neglect. After early success with Poor Cow (1967) and the hugely acclaimed Kes (1969), his career suffered from poor distribution, censorship, and cancelled commissions through the 1970s and 1980s. It was in the doldrums when Hidden Agenda, a docu-drama about police corruption in Northern Ireland, won the 1990 Special Jury Prize in Cannes. Next year, Riff-Raff (scams and camaraderie on a London building site) picked up the Felix Award for Best European film. In 1993, Raining Stones (a hard-up Lancashire father tries to buy a Holy-Communion dress for his sweet daughter) won another Special Jury Prize.

The British film community, as though roused from a great slumber, blinked at Loach. Why was he being praised by continentals? Was he, in fact, quite good? Were his films actually human dramas with pathos and humour, rather than (as caricatured) grimly dirigiste socialist tracts about the beleaguered working class?

As though refusing to be courted by the mainstream, Loach's next offerings were almost aggressively uncommercial: Land and Freedom, in which an unemployed Liverpudlian Communist miner goes to the Spanish Civil War in 1936 and encounters tragic infighting (and a 20-minute dispute about ideology) among the comrades; and Carla's Song (1996), in which a Glaswegian bus driver falls in love with a Nicaraguan refugee and gets a brisk education in Central American politics. Loach's refusal to compromise was admirable – and his more recent work has grown more subtle, accessible and humorous.

There's a useful aide-memoire for the modern cineaste which runs: "If it's blokes on a coach/ Then you're watching Ken Loach/ (If they're eating their tea,/ It must be Mike Leigh)," and, sure enough, The Angels' Share has a long-haul vehicle in the second reel, taking a rambunctious band of Scottish neds [low-lifes] on a trip to the countryside. Written by long-term collaborator Paul Laverty, it's billed as a "bittersweet comedy," and has a happy ending. Wasn't this a huge departure for him?

"Not really," said Loach. "They say comedy is just tragedy with a happy ending. What you have to do is capture some truth about the way people are, how they interact, the possibilities they have. One story may end in disaster and one happily – but they're the same characters. You try and capture them in the same way."

The story centres on Robbie, a young Glaswegian tough nut with a family history of violence, feuding, and doing time at Her Majesty's Pleasure. He's given 300 hours' community service for fighting. And when – bruised and battered by his girlfriend's horrible father – he holds his new baby son, he vows to change his life. Through his supportive supervisor, he learns about – of all things – malt whisky. With an awkward squad of fellow community servers, he hatches a plan to pull off a heist on a million quid's worth of Scotch and live happily ever after.

Loach and I meet in London's Soho in a room above a whisky shop. In the flesh the great director, 75, is slight, shy and very polite, miles from the radical firebrand his films suggest he must be. His eyes have a nervy melancholy as though he's exhausted from 40-odd years of trying to wake people up to everyday realities.

"No, I don't think we're pessimistic," he says, "we" being him, Laverty, and Rebecca O'Brien, his producer. "I think people are endlessly resilient, and funny and inventive. You just hope, in filming, to be realistic about the way society and economic circumstances drive people into corners."

He likes to use non-professionals in his movies, to convey a sense of realism. How had he cast the film? "We must've seen several hundred guys. We might go to a college and see 30 or 40 people in a day. You soon get a sense of whether someone can make you smile and make you sad for them." He chose Paul Brannigan as Robbie for "the sense that he's packed a lot into a short life. He knows the score. He knows how people are."

I asked him about a scene where Robbie viciously attacks a blameless man and leaves him blind in one eye. Hitherto, we've seen him fight to defend himself. But, in this scene, he becomes a nasty little shit. Didn't he risk losing the audience's sympathy? "The reality is that people have done some very ugly things," said Loach defensively. "And he was in a Young Offenders' Unit for a long time so he must have done something pretty awful...

"We talked about this scene a lot. In the end we decided we didn't want to sentimentalise him. He's got a long journey to go on, as a character. And it's good to pull the audience in different directions." Loach and Laverty have collaborated on eight full-length films, from Carla's Song to Looking for Eric (with Eric Cantona) and 2010's Route Irish. The reason Loach makes films set in Scotland is because Paul is a west-coast Scot.

"One of the first principles I imbibed, back in the BBC in the 1960s, is that you follow the writer, whatever you're making. So I worked in south Yorkshire [on Kes] with Barry Hines, in Liverpool and Manchester with Jim Allen [on Hidden Agenda, Raining Stones and Land and Freedom] and the west coast of Scotland with Paul. And in Ireland [on The Wind That Shakes the Barley] because his family has Irish antecedents. I think what a writer hears in his head gives the dialogue veracity. When the characters in this film were doing scenes, they were using Paul's dialogue but thinking they'd made it up." Why did he keep returning to the plight of the desperate, trapped and unsuccessful young, and did it hark back to his own experience?

Loach emitted a bitter laugh. "No, I was extremely lucky. I was of the grammar-school generation. The ones who got through were fortunate to go to university, but 80 per cent of the kids in Nuneaton, the town I came from, were written off at 11." This was the signal for an extended, clearly heartfelt rant about the young being unable to fulfil their potential. "The despair in those kids... even the ones who're in work are on short-term contracts, casual labour. They've no sense of being able to look forward to a future with a family, a house and security. What we've done in this wreckage of young people is shocking."

I wondered what kind of kid he was at 18. "This was the 1950s. We weren't teenagers; they didn't exist. I was very boring, I was keen on classical music. We lived quite near Stratford-on-Avon, and my friends and I would go to watch Laurence Olivier and Vivien Leigh. We were impertinent and cheeky, but it was a very different time. The idea of teenagers came just after I was one. At 18, I was in the school sixth form, trying to get to university. At 19, I was doing National Service and being shouted at." Surprisingly, he wasn't interested in cinema.

"I was stage-struck, I used to put on plays all the time." But the screen, I said, what did you respond to on screen? "I liked documentary still photography, like Cartier-Bresson and Bill Brandt," he said, "and the novels of John Wain, Alan Sillitoe, Stan Barstow and DH Lawrence." Realism, in other words. Realism, grit, in-your-face drama, and a touch of didacticism. Of which Mr Loach has been, for 40-odd years, the unregenerate, unsinkable champion.

'The Angels' Share' is out in the UK on 1 June