Mike Leigh: 'Me? Miserable? Nonsense!'

He admits that his new film 'Happy-Go-Lucky' has put a smile on his face – but, says Mike Leigh, woe betide any actor who reveals the director's 'trade secrets'

One hates to harp on about Mike Leigh's reputation as a curmudgeon, but there's undoubtedly a certain, let's say, brand recognition attached to it. The 65-year-old director scowls out from the cover of his new DVD box set – designed by Toby Leigh, one of his two sons – in a passport-booth mugshot that makes him resemble a man who once planned an unsuccessful minor British bank heist. You suspect Leigh quietly relishes his image. On the table in front of him at his Soho office, his coffee mug bears the legend "Crabbit": a Scottish dialect word meaning "ill-tempered, grumpy, curt, disagreeable". "It was a gift," Leigh says, "from a humorous actress who used the word when talking about a character. So, in fact, it's not about me." Leigh is perfectly affable and voluble. But he can be "blunt and Northern", as he puts it, slipping into a sitcom blunt-and-Northern accent.

There's no denying that Leigh's films have provided some of the most unmitigatedly stark episodes in British cinema – ever since his 1971 feature Bleak Moments, a polar study of English emotional isolation. Since then there have been, among others, Naked (1993), in which David Thewlis, as the last of the great Angry Young Men, haunts a stygian London night; the sobering picture of post-war Britain in the Venice prize-winner Vera Drake (2004); and, in 2002's All or Nothing, the most harrowing scenes of marital incomprehension seen outside of Ingmar Bergman.

So, is the world ready for Mike Leigh in upbeat mood? When his new film Happy-Go-Lucky premiered in Berlin earlier this year, Leigh surprised the press conference by announcing it was time "to reject... the growing fashion to be pessimistic and gloomy".

Hunched in his armchair in his oddly mon-astic khakis, Leigh insists, "There is no question that these are disastrous times, we're destroying the planet and we're destroying each other. But notwithstanding that, people do get on with it, basically." Getting on with it is one of the strongest approbations in the Leigh lexicon. In Happy-Go-Lucky, the term applies to Poppy (Sally Hawkins), a London primary-school teacher whose enthusiasm and exuberance are unquashable, even in the face of life's horrors. "It's the Poppies of this world, the teachers," Leigh says, "who believe enough in the future to get out there and nurture kids. I don't particularly like the idea of positivism. On the other hand I'm quite amused by the notion of being anti-miserabilist. Not least because I've been accused of being miserabilist in other films – which is nonsense."

Happy-Go-Lucky is hardly the first Leigh film to display a healthy degree of joie de vivre: not a few viewers emerged fairly floating from his 1999 film about Gilbert and Sullivan, Topsy-Turvy. The new film, however, maintains the upbeat mode as consistently as Leigh has ever done – although happiness isn't necessarily its topic, he says.

"The title evokes a spirit more than describes it. To describe Poppy merely as being happy, like she's eaten a load of magic mushrooms or smoked a lot of dope, is ridiculous. She's not merely happy as a bland condition – she's sussed and focused and grounded and knows how to deal with things in her own quirky but quite proper and serious way."

A happy character who is neither an irritation nor a holy fool: surely one of the toughest challenges in drama. But Poppy comes alive in a crackling performance that won Sally Hawkins the Best Actress award in Berlin. It's her third film with Leigh: she was the council-estate temptress in All or Nothing and the upper-crust girl who got pregnant in Vera Drake. When did Leigh first realise quite how good Hawkins was?

"Straight away. In fact, when she walked into the room, first time I met her. She's very sharp, very funny and very good company – a gas, basically. She's incredibly generous: even now that she knows she carries the whole picture, more than anyone's ever carried the whole picture, she still prefers to think of it as an ensemble piece."

A haze of rumour and mystique has long surrounded Leigh's unique working methods, which he has developed over five decades in theatre, television and film. It's generally realised, however, that the process involves intense improvisation, research and close collaboration with his actors. As he puts it, "The journey of making the film is a journey of discovery as to what the film actually is." If you want a detailed account of what this entails, you can find it in the new book Mike Leigh on Mike Leigh, an exhaustive set of interviews in which he reveals all about his methods. Or perhaps not all. I make the mistake of starting a question, "Having read the book and knowing how your process works..." to be met with a bellow of derisive laughter.

In fact, the book amply demystifies the Leigh methodology, which comes across as pragmatic, level-headed and rhetoric-free, with codes of practice including the rule of never letting actors discuss their characters in anything but the third person. Any talk about players getting too close to their parts is firmly discounted. "The whole thing about people becoming the characters doesn't happen, and is not on," Leigh tells me.

Even so, at several points in the book, Leigh declines to reveal certain "trade secrets". "I refuse to," he says. "The truth is, I don't want to appear to be enigmatic or obscure for the sake of it. However, in actual terms, there's stuff that goes on that can only be understood by people taking part in it."

What emerges from the interviews is that each piece derives directly from, and only from, the collaborative work that produces it, work which begins with the casting. "I cast intuitively," Leigh tells me. "I get people and I don't know what I'm going to do with them." In Happy-Go-Lucky, he knew he wanted to work with the extraordinary Eddie Marsan, who had been in Vera Drake, but neither of them knew he would end up playing the embittered, ranting driving instructor Scott, a breathtakingly intense knot of obsessive dogmas and arcane mnemonics. "We just got on to the notion of a totally eclectic magpie guy who reads and Googles a lot of stuff, and the thing was to say, 'We amass all this but we don't make the mistake of having him understand it.'" The result is a priceless and quite terrifying tragicomic creation.

Leigh works strictly on a need-to-know basis, with actors knowing only what their characters do, no more. During the preparations for Vera Drake, the scene culminating in Vera's arrest emerged from a 10-hour improvising session, at the end of which the actors playing the Drake family were astonished by the arrival of actors playing police.

Not that Leigh is interested in traumatising his casts. "People who don't have a sense of humour can't do this. For me, it's about getting a gang of people together who can really work together, and one of the things they've got to be able to do is like each other. Love each other, without getting too soppy about it." But the process must make for some surprises when his actors finally get to see their work on screen? "Of course. Every time. Because they never know what's in the whole film until that occasion. That's one of my favourite things in the whole process – I give them a private screening, and then I take them off and we get drunk. And it is always a total revelation."

'Happy-Go-Lucky' is released on Friday. 'Mike Leigh on Mike Leigh' (Faber & Faber, £12.99) and 'The Mike Leigh Feature Film Collection' DVD set are both available from Thursday

Five essentials in the Mike Leigh canon

Bleak Moments, 1971

Starting life as a play, this London drama explores an enduring Leigh theme: "The whole business of received behaviour"

Abigail's Party, 1977

Essentially a filmed play, Abigail's Party has a special place in the British cultural consciousness. Leigh regards it as "the cuckoo in the nest among my television work...'

Naked, 1993

Leigh's darkest piece, Naked starred an incandescent David Thewlis as a man on the run, with 1,000 theories buzzing round his cranium

Topsy-Turvy, 1999

The Leigh film no one expected: a 152-minute panorama about the creation of Gilbert and Sullivan's The Mikado. Is it a thinly veiled portrayal of Leigh's own directing processes?

Two Thousand Years, 2005

Leigh's last stage venture, performed at the National and recently revived in New York. This family drama looked back to Leigh's own Jewish origins. One of his most directly political pieces