The big match: What happened when 'good socialist' Ken Loach met Eric Cantona, a legend of one of the world's richest football clubs?

Filming is over for the day, which is just as well because everybody who's still on set, observing the spectacle unfolding in front of them, has an identical look in their eye. It's an expression that great directors such as Ken Loach seek to discourage in their actors; one which says: can this possibly be real? Loach himself is looking on with amused disbelief. In front of us, on the lawn of a detached house in north Manchester, are 50 Manchester United supporters, most in the scarlet shirt. Each is wearing, or holding, a rubber Eric Cantona mask. Some are wielding croquet mallets. At the heart of the mêlée, his head tilted back at a suitably regal angle, is Cantona himself.

At 6'2", the footballer is taller than most of his admirers, and his face is clearly visible as the fans break into "Ooh-ah Cantona", their favourite hymn to their hero. They sing as if they're never going to stop: loud, with feeling, and, most disturbingly of all, almost in tune. Rachida, his wife, is standing next to me. "Look," she says. "He's crying."

If there have been two incidents which have symbolised the bond between the big man from Marseille and the city of Manchester, they are the kung-fu kick which Cantona delivered in response to the racist taunts of a so-called supporter at Crystal Palace, in January 1995, and the penalty he dispatched against Liverpool nine months later, on his return after suspension. The celebrations that followed that goal were a tangible demonstration of the loyalty shown by both parties following that FA punishment, when either club or player might easily have walked away. Cantona purists might mention his 1996 strike against Sunderland but, for most of us raised in the red half of Manchester, those were the two iconic moments. I think everyone present would agree that the tears Eric Cantona shed this afternoon, on a threadbare lawn in Worsley, constitute a third. Even though it's started to rain, and he has no coat, Cantona stays until every fan has had his picture taken with him, and every shirt has been signed.

"Did you notice," I ask one of the supporters, "that he was crying?"

"Well... yeah," the man says, as if he's informing on a friend.

"You wouldn't get Ronaldo doing that."

"We wouldn't do this," he replies, "for Ronaldo."

Ken Loach has been shooting the climax of his forthcoming film Looking For Eric, in which a postman (Steve Evets) , also called Eric, whose life is disintegrating, has visions of the ex-footballer, who plays himself. The scene they filmed today required the 50 masked Cantonas, recruited mainly from FC United (the breakaway club formed in 2005 by Manchester United supporters, following Malcolm Glazer's controversial takeover of the Premiership team), to trash a house with mallets, baseball bats and golf clubs.

Earlier in the afternoon, the supporters had lined up on the lawn, preparing to demolish the living-room, when a people-carrier pulled up in the drive. Cantona and Rachida emerged and walked up the path, followed by the actor's brothers, Joel and Jean-Marie. Observing the effect of Cantona's arrival on Loach's extras, who were ordered to hold their positions, was rather like watching a troop of Knights Templars who have been commanded not to break their battle formation even though they've just seen Jesus stroll by, swigging from the Holy Grail.

While the director prepares the fans for the next scene, Cantona takes up a position close to where I'm standing, next to Loach's sound man. I shake Cantona's hand and give him a copy of the French edition of one of my books. I brought it specially: I have to admit that, to an extent that I haven't experienced since I was with the late George Best, all hope of journalistic objectivity has vanished. "Is it fiction?" Cantona asks, in his Marseille-accented French, assuming from the title ' on the book's jacket that I must be French. I tell him it is, and that one sequence takes place in his home town.

"Where in Marseille?"

"At La Bricarde; it's in the 15th arrondissement; you know where La Castellane is ..."

La Bricarde is one of the most challenging housing estates in the city. The footballer, who grew up in a more comfortable area on the other side of Marseille, but played football on the beach below these so-called "difficult" areas, smiles politely.

"I know," he says, "where La Bricarde is."

Twenty yards away, on the lawn, the red army is restless. Every eye is on him.

"I'm so proud that they still like me," Cantona says. "United fans are so loyal. We are bonded forever. I am still in love with United."

Words like aura and charisma have been debased to the point that it is extraordinary when you meet somebody who genuinely has both. Those dark eyes sear through you. Meeting Eric Cantona reminded me of an interview I once had with an American carnival performer who was accompanied by an untethered pure-bred wolf. With Cantona, you get the same sense that – as is recommended practice when dealing with that animal, which regards a direct stare as a provocation – it might be safer to look at him sideways on.

Where her husband is concerned, Rachida believes, "behind the man who dares, there is also a man who doubts".

"I've always been paranoid about the telephone," Cantona says. "Meeting one to one, I can judge whether the other person is open. On the phone, it's so easy to lie. I prefer speaking face to face."

Friends say his trust is not easily gained but that, once gained, you have it forever.

"As Serge Gainsbourg remarked," says Cantona, "I can count my friends on the fingers of Django Reinhardt's hands."

If your only memory of Cantona, now 42, is his appearance in the 1998 film Elizabeth, you might be forgiven for not taking him seriously as an actor. More recently, he has confounded critics who ridiculed his new career. It's true that, in the 1998 film Mookie, there is a scene where Cantona has to wheel an alcoholic monk out of a Mexican bar, using a pushchair that has become available because Eric has temporarily lost his talking chimp. But Mookie is what it is: a comedy for children, and Cantona doesn't let down his seasoned co-star, the late Jacques Villeret, who worked with directors such as Jean-Luc Godard, Bertrand Blier and Claude Lelouch.

The real proof of what Cantona can achieve is in Thierry Binisti's 2003 film L'Outremangeur (English title: The Over-Eater), in which he plays Richard Séléna, a bulimic police inspector. Séléna, 160kg, eats agricultural quantities of food every evening, in tears, alone in his baroque mansion on a cliff overlooking Marseille. When he discovers that Elsa, a young woman of North African origin, is a murderer, he agrees to protect her on condition that she walks up to accompany him over dinner, every evening. Improbable as this may sound, in L'Outremangeur, Cantona's performance in a fat suit is deeply moving. If you didn't already know, there's no way you could guess which member of Binisti's otherwise experienced cast could work miracles with a football, except for the fact that, when the inspector suffers a heart attack, the corridor leading to the light, in his near-death experience, is decorated in Manchester United colours. It was on L'Outremangeur that Cantona met Rachida Brakni, who played Elsa, and became his wife in June 2007.

"I'm ugly in that film," Cantona says. "Rachida is young and beautiful. I can't bear my reflection. But I fall in love; I look into her eyes and for the first time in my life I've found the only mirror I can look into."

He has two children from his first marriage, to Isabelle Ferrer. (A new, comprehensive biography, Cantona: The Rebel Who Would be King, by leading French writer and broadcaster Philippe Auclair, is published in August.)

The prevailing atmosphere on most film sets is one of boredom punctuated by murmured resentment about the privileges extended to the stars. On a Ken Loach shoot, there is none of this. The director, 72, softly spoken and retiring as he may appear, commands immediate respect. His combination of thoughtfulness, diffidence and effortless authority means that he comes across rather like a professor whose jacket is known to conceal a .44 he has never had to use. If you want to know what happens if you underestimate Loach (once described by The Times as "worse than Leni Riefenstahl"), you might watch the YouTube footage of his recent Newsnight debate on the miners' strike, with Nigel Lawson. Loach, who trained as a lawyer, gently skewers Lawson who, with his sagging jowls, looks increasingly like a bewildered pantomime dame who has wandered into the wrong studio.

During the filming of Looking For Eric, Loach tells me, Cantona exhibited none of the arrogant behaviour that enemies might have predicted. "If anything, it was the reverse. He showed real humility. He'd often ask: 'Was I OK? Really? Are you sure?'"

And was he? "He is very, very good."

(If you watch the out-takes on DVDs of Cantona's French films, it's noticeable that, whereas experienced cast members snigger when they ruin a scene, the former footballer looks mortified at his mistakes.)

I've never met Ken Loach before, even though, as I tell him, he was the first name I ever suggested, as a freelance, as a subject for an interview. "The editors I spoke to at that time had no interest in you whatsoever. Their attitude was, who could possibly care about this Socialist dinosaur who once made a film about a bird?" [Kes, Loach's adaptation of a Barry Hines novel about a Barnsley schoolboy who escapes an impoverished existence by flying a kestrel, was released in 1969.]

"When was this?"

"Late Eighties."

"As a company," he says, "we've survived through our contacts with Europe; through co-productions. Without that, there's no way we could have done the work we have."

"One of my best memories is going to see a double bill of Riff-Raff and Raining Stones at a small neighbourhood cinema in Barcelona. The audience weren't people who'd necessarily go to the cinema regularly. The place was packed. At the end, they all stood up to applaud."

"This cinema ..." he says. "Where was it?"

"Calle Verdi."

"Is it still there?"

"As far as I know."

Loach is well-practised at guiding conversation away from his own achievements.

Looking For Eric, while far from being a light comedy, isn't the kind of territory you would expect the director to explore. A writer from The Guardian recently told Loach that the film reminded him of Play It Again, Sam, in which Humphrey Bogart materialises to give advice to Woody Allen.

If that comparison is an imaginative one, Looking For Eric does, unquestionably, have echoes of another work. In Alan Bleasdale's 1984 TV series Scully, the eponymous hero, played by Andrew Schofield, is comforted in moments of stress by visions of Liverpool legend Kenny Dalglish, who appears as himself. In Looking For Eric, the actor you will probably best recognise is John Henshaw. A former bin-man who plays the bumbling manager in the Post Office's recent commercials, ' Henshaw was given his first break by Bleasdale, in the classic 1991 Channel 4 series, GBH.

That said, you have to ask how much even Shakespeare would have suffered if "pre-loved" dramatic concepts (eg regicide) could never be replicated. "Oh, please," Loach told The Guardian, "don't compare this to other films."

Kenneth Loach grew up in Nuneaton, Warwickshire; his father supervised the maintenance shop in a machine-tool factory in Coventry. He read law at Oxford, then seems to have drifted for a period. He spent two years "as a typist in the RAF" and worked as a supply teacher. For a year, he directed repertory productions in Northampton. ("Our Miss Marple had a wobbly memory. Some nights she forgot the name of the murderer. Audiences left mystified.")

Loach then enrolled on a BBC training programme. One lecture was called "What to do With Your Cameras". He directed episodes of the police series Z Cars and achieved national prominence in 1966 following the transmission of Cathy Come Home. The TV drama charted the descent of his main character, played by Carol White, from the joy of young motherhood to abject homelessness. The play galvanised the development of the homeless charity Shelter. Loach, however, has repeatedly expressed disappointment at the legacy of Cathy Come Home.

"We stimulated energy and it led nowhere. It persuaded a few people to send a few shillings to Shelter. That's all. I would have liked Cathy to lead to the nationalisation of the building industry and home ownership."

There are still people who, when you mention the name of Loach, wince at the thought of a dose of worthy realism. "Not so long ago," I tell the director, "I heard you interviewed on BBC Five Live by someone who used the word 'gritty' so often in the first three minutes that you had to ask him to stop."

"I don't recall that conversation. It has happened."

In terms of the subjects which have attracted him – they include miners, dockworkers, builders, the Fylde coast and the urban dispossessed – Loach is strongly reminiscent of his contemporary Colin Jones, who has been described as "the George Orwell of British photography". Although Loach, like Jones, comes from the southern half of Britain, both men have gravitated towards the north, whose working communities each has approached with the fresh sensibility of an empathetic outsider. (Loach's 2007 BBC Radio Three documentary on Blackpool is an unhailed triumph.)

For many years, people have tried, unsuccessfully, to persuade Loach to articulate his credo. I'm not sure he could do better than a passage that Jones hung alongside his photographs at a recent London exhibition: an excerpt from Norman Mailer's report on the 1983 General Election. "Michael Foot," Mailer wrote, "had a cogent point of view, at least. It said: we are not here in the world to find elegant solutions, pregnant with initiative, or to serve the ways and means of profitable progress. No, we are here to provide for all those who are weaker and hungrier, more battered and more crippled than ourselves. That is our only certain good purpose on earth, and if you ask me about those economic problems that may arise if the top is deprived of their initiative, I would answer: 'To hell with them. The top is greedy and mean and they will find a way to take care of themselves. They always do.'"

Though he has matured in a career spanning more than four decades, Loach is unusual in that, where certain aspects of his working methods are concerned, he arrived fully formed. Long before Kes, he had espoused the practice of showing actors only the next few pages of a shooting script, so that events come as a surprise to them. David Bradley, who plays young Billy in Kes, didn't have to feign distress when he found the body of a bird which he believed to be the kestrel he had been working with for weeks. When Julie Brown received a visit from loan sharks in Raining Stones, the actress had no idea that her wedding ring would be taken from her in a scene of almost unwatchable brutality.

On the set of Looking For Eric, I had lunch with scriptwriter Paul Laverty. "In the scene where Eric [the postman] sees Cantona for the first time," Laverty told me, "he had no idea of what was coming. You can see the amazement in his eyes." Loach's ability to get actors to conspire in this way, allied to a unique gift for fostering improvisation, and identifying acting potential in people with no experience, make him, I would argue, our greatest living cinema director.

Ken Loach, who has little enthusiasm for volunteering confidences, has rarely spoken about his memories of 2 May 1971, when a wheel sheared off a car being driven by a Harrow publican on the M1, precipitating the crash in which his five-year-old son Nicholas, and his wife's mother, were killed. (He and his wife Lesley have four surviving children.) He didn't work for a year after. By 1980, while he had completed an impressive body of television work, including Days of Hope, his 1975 BBC series about the years leading up to the General Strike, he hadn't made a cinema film for almost a decade. It was, Robert Altman remarked, "a disgrace".

Undeterred by the miserable state of the Socialist movement in the 1980s, Loach never wavered from his belief that "the only class worth connecting with is the working class".

"He gives a respectable platform," wrote Nicholas Wapshott in The Times, in 1981, "to those who are regularly called 'wreckers, troublemakers and Trots'." To which I can hear Loach muttering: "Regularly, Nick? Maybe in your house."

Even the director's most optimistic admirers couldn't have foreseen his extraordinary renaissance in the 1990s. Land and Freedom, his 1995 masterpiece about the Spanish Civil War, was written by long-standing collaborator, Jim Allen. Allen, a former miner, died in 1999. The torch he dropped has since been carried, brilliantly, by Paul Laverty. Laverty, born in Calcutta and raised in Glasgow, has, like Loach, a background in law. His unorthodox film apprenticeship also includes a philosophy degree and several years spent monitoring human-rights abuses in Nicaragua, in the 1980s. The writer, who appears as an actor in Land and Freedom, has unquestionably encouraged a wider international dimension in Loach's work. Carla's Song, their first collaboration, released in 1996 (the moving story of a romance between a Glaswegian bus driver and a Sandinista) took Loach to Nicaragua. Laverty initiated, and wrote, Bread and Roses, their ambitious 2000 production about the exploitation of Mexican cleaners in Los Angeles.

"We have governments like Mr Blair's," Loach said, before Bread and Roses was shown at Cannes, "who talk about flexibility of labour but are continuing the policies of the right, which are all about the rights of the employer." The Government delegation boycotted the screening.

Laverty also wrote The Wind That Shakes the Barley, which follows two brothers from Cork, during and after the Irish War of Independence. The film won the 2006 Palme D'Or at Cannes. In his recent collaborations with Laverty, Loach has increasingly travelled north of the border, but each of their ' films has remained faithful to the director's fundamental instinct – namely, that you can illustrate universal truth however localised the setting.

There are moments when Loach, Laverty and Rebecca O'Brien, Loach's long- standing and distinguished producer, sound less like hardened professionals, more like amiable co-conspirators. On the set of Land and Freedom, O'Brien remarked, without irony, "everybody was a good Socialist".

At lunch during the shooting of Looking For Eric (served at Swinton Cricket Club, a friendly location that Loach, a supporter of Warwickshire and Bath City FC, chose as his HQ) everybody – including actors, Loach, O'Brien and Laverty – queues up like everyone else. Nobody has a trailer to sulk in. It was an ethos Cantona warmed to immediately.

"He became one of us," says Loach. "He was literally one of the lads. I suppose it's something you learn in football; how to be part of a team."

After the filming, I met Sir Alex Ferguson at Manchester United's training ground. Ferguson explained how important this sense of belonging is to Cantona, who had experienced many difficulties in France. (Some, it has to be said, began when he called his national coach Henri Michel "a shitbag".)

"If there was ever one player, anywhere in the world, that was made for Manchester United, it was Cantona," Ferguson told me. "I think because he had travelled to so many different countries. There's a bit of the gypsy in some people. He'd been searching all his life for somewhere he could look at and feel: this is my home. And when he came here, he knew: this is my place. You could just tell. He was calm. His training performances were fantastic. He got on with everybody."

Ferguson recalls a recent conversation with club captain Gary Neville. "Neville says: 'You know what I really loved about Cantona?'" The manager pauses. "I have to admit that this is not a great story in terms of the way I run this club. Anyhow, Gary said: 'Occasionally, we'd have a night out and hide it from you. We'd all say, "Don't tell anybody anything about this; especially where, or at what time, we're meeting." And then during training, Cantona would say: 'Right! I'll see you all later! At nine! In... such and such a place.' And they were all going: 'Shut up! The boss is here!' The point is that he was so proud and so keen to have nights out with the boys. And he wasn't a big drinker, Cantona. A beer. A glass of wine. But he loved being part of that culture; part of a group; that feeling of being together. And that," Ferguson continues, "was something he'd never experienced in France."

"It's funny you say that, because when he shakes your hand and looks you in the eye..."

"I know," Ferguson says. "It's daunting."

Loach – who, in Kes, wrote probably the best footballing scene in British film, refereed by the late Brian Glover – has played down reports of the United manager's regard for his films. Talking to Ferguson, though, it's obvious that his interest in Loach is informed and intelligent. He was especially enthused by The Wind That Shakes the Barley.

"The thing about that film is the way it captured that defining moment in Irish history," Ferguson says. "I'm thinking of that scene where news of the treaty had come through; when Michael Collins came back from London [with a peace treaty]. That meant the division of Ireland. In that room you had 20 people giving their opinions about what should be done. It meant the division of families; the point at which brother kills brother. If you remember that scene, it was amazing. Absolutely fantastic."

Ferguson's perceptive take on Loach's work is interesting, not least because there is a default assumption in some circles that a football man who exhibits any cultural interest should be regarded as a buffoon until proven otherwise. Few have suffered from this prejudice more than Cantona, perhaps because his still-hesitant English makes it hard for British reporters to tell when he's joking.

His sense of irony – on or off screen – is subtle and well developed.

The title of Cantona's 1993 autobiography, Un Rêve Modeste et Fou (literally, A Modest, Crazy Dream) is taken from a work by the Communist poet Louis Aragon. When he discusses his enthusiasm for art – discovered first in the studio of his father Albert, a psychiatric nurse and amateur painter, and nurtured in galleries displaying Munch and Picasso – he is insightful and straightforward. It's the same when he discusses his affection for the film director Maurice Pialat, or the singer Léo Ferré. If you've come across Ferré's songs, or the great films of Pialat, such as Under Satan's Sun, in which Gérard Depardieu gives one of his finest performances as a priest who meets the devil, you will know that these are simply not the kind of artists anybody would pretend to appreciate in order to impress. No more than they would direct, as Cantona has, a short film version of poet Charles Bukowski's story Bring Me Your Love.

In Marseille, before he first came to England, Cantona visited the house of the late industrialist Jean-Luc Lagardère. "On his wall there was a painting by Miró, one of my favourites. I could hardly believe it was the original. Lagardère gave me a book on Miró. So I was holding a print of the picture, looking up at the original. Afterwards, while I was waiting for a cab, I tried to calm myself down."

Cantona's philosophy, widely portrayed as risible, is not that far from Loach's. Which English footballer would have sought to house his family in modest accommodation, as Cantona did, first in the ethnically mixed area of Roundhay, Leeds (where he played for less than a year), then at Boothstown, near Manchester? Which domestic star can you image publicly extolling the courage of the International Brigade in Catalonia? (Cantona moved to Barcelona, home of his grandfather, after leaving Manchester, before returning to France.) Which player would voice contempt for Bernard Tapie, crooked former chairman of Olympique de Marseille, quite so frankly?

"Where there is money," Cantona believes, "you have cheats. The two go together." While neither Ken Loach nor Eric Cantona has been driven by the pursuit of wealth, they risk, despite themselves, making a fortune with this film. I make this point to Loach, a few months after the filming, when we meet in a London editing suite, where he's cutting Looking For Eric.

"Aside from your own constituency," I suggest, "if even one in six United fans around the world goes to see this film, just imagine..."

"I never approached this," Loach says, "with that in mind."

He's editing a scene that begins with a family lunch at a house in Chorlton, south Manchester. It explodes into something resembling the more alarming scenes from Raining Stones. One actress looks terrified.

"Did she know this was coming?"

"No."

I can't help being struck by the customary gentility of Loach and the mayhem unfolding on the screen in front of us. He still works, as he always has, with his trusted editor, cutting film with a razor blade. Each section is patiently numbered, and filed.

"There are one or two people in Hollywood who still edit like this," Loach says. "One of them is Steven Spielberg."

"Let's look ahead," Loach says, "and see if we find any good bits."

"Any good bits? I repeat. "What other legendary director would say that? Spielberg? Scorsese?"

The sequence, when he's finished it, is wonderful. Extraordinarily for such a robustly eventful narrative, almost every shot, when frozen on screen, is a beautifully composed still picture. That said, my most striking memories from this experience are of that day last summer, in Worsley. At one point, Loach went in to examine the living-room after it had been trashed by the fans who, once they were let loose with their weapons, seem to have experienced a degree of what is commonly called "mission creep".

"I'm not sure," Loach said, as he examined some fragment of mirror, TV set, or table, "that this was supposed to go..."

At the end of the day's filming, I'd shaken his hand and thanked him for allowing me on the set. "You're welcome," he said. "Just one thing."

"Yes?"

"The next time in your life when there's a day that you do something utterly ridiculous; some day when you risk making a complete fool of yourself," Loach adds, "please call me. I'd like to come along."

'Looking For Eric' screens at the Cannes Film Festival next month and opens here in June