At 65 years of age, it’s good to see that Mike Leigh has learned nothing about handling the press. By turns blustery, crabby, contrary, humourless, paranoid and evasive, Leigh belongs to that generation of no nonsense, taciturn northern men epitomised by ever irritable TV ‘twitcher’ Bill Oddie.

Along with Ken Loach, Leigh is often perceived as one of the forefathers of a certain kind of British film realism which developed out of the kitchen sink dramas of the early 1960s (Saturday Night and Sunday Morning, This Sporting Life, A Taste of Honey) and the relative freedom afforded young playwrights and filmmakers by the BBC in the late 60s and early 70s. It’s a moniker he clearly dislikes, perhaps because it infers decrepitude of years. When I express surprise that he has made a film as joyous, youthful and humane as his newest, Happy-Go-Lucky, at this stage in his career, his reply is frothy: ‘Everyone else is more preoccupied with the lateness of my career than I am. It seems like a complete red herring to me. I suppose I could look around at people that were born the same year as me, who are behaving like old men and old women in a way that I’m not.’ Pausing, he adds: ‘But I don’t want to get smug about it, I’m only even talking about it because you asked.’

Leigh’s new film, his tenth cinema feature was, he impatiently points out, made the way he always makes films. He says, ‘Firstly I collaborate with a gang of actors and create the characters and relationships. Then I share my feelings with the cinematographer and the designers and work out what it’s going to look like, feel like and all of that and then I go out there and I make the film up as I go along. I discover by the journey of making the film, the structure of the film.’

Happy-Go-Lucky follows the adventures of Poppy, a kooky 30-something primary school teacher living in contemporary London. The character is played by Sally Hawkins, who took the Silver Bear Award for Best Actress at this year’s Berlin Film Festival for her efforts. Poppy is open, kind, funny, bawdy but also responsible and comfortable with being single. She works hard, plays hard with her flatmate and best friend Zoe (Alexis Zegerman), visits her family, takes driving lessons with psychotic teacher Scott (Eddie Marsan), attends flamenco and trampoline classes and starts a new relationship with big-chinned child social worker Tim (Samuel Roukin). She has time for everyone and everyone adores her in return.

More French new wave than British kitchen sink, Poppy’s cinematic antecedents are Juliet Berto’s kinky comical magician in Jacques Rivette’s Celine and Julie Go Boating and Jeanne Moreau’s Catherine in Truffaut’s Jules et Jim. With her half glass full attitude, Poppy is the mirror opposite of David Thewlis’ pessimistic and nihilistic Mancunian ne’er do well Johnny in Leigh’s most contentious film to date Naked (1993).

Leigh finds nothing strange in this shift towards more positivist values. His look at life since the end of the Thatcher years has been marked by what he calls a ‘fairly three dimensional and real’ aspect, and as far as this film is concerned he believes that ‘Poppy’s spirit is positive and you get something very much out of that. I think that Vera Drake’s got a positive spirit too but circumstances affect what happens to her in a way. I guess it’s too simplistic to say it’s optimistic compared to all my other films. Perplexingly, Happy-Go-Lucky seems to be getting a bad press because of the good things that happen in it. But I could make a long list of good things that happen in many of my films.’

Unwilling to unravel the subtexts or dig out the ley lines that run through his oeuvre, Leigh pours scorn on my suggestion that Poppy is basically a prophetic idiot savant exposing the greed and self absorption eating into the heart of life in Britain; or that he deliberately cast the brilliant Hawkins for her resemblance to the late great actress Katrin Cartlidge who played another flaky working girl in his underrated 1997 drama Career Girls. He even gets a little bit tetchy when I ask him about the motivation for, and the development of, certain key scenes in the film. Of a memorable sequence in which the inebriated Poppy wanders through an industrial wasteground with an insane vagrant, Leigh finally relents that: ‘There was the memory of an experience there of “god this is weird, where am I?”’

Leigh becomes more animated on the subject of Scott, the uptight and unhinged driving instructor in the film, whose prejudicial rants and isolationism contrast sharply with Poppy’s beguiling sense of inclusion and kindness. He says: ‘There is a line of humorless paranoid people in my films and he is the latest in that long line. For me the thing that’s interesting about Scott is that all this stuff he’s read, it’s all slopping around in his head but he doesn’t understand any of it really, he doesn’t make connections, he’s not perceptive really, he’s certainly not in touch with his own emotions, he’s got all kinds of fancy ideas about teaching and he’s the worst teacher in the world basically, and of course Poppy’s sense of humour brings out the worst in him in a way because she parodies him. But not unsympathetically, it is just her way of dealing with the situation.’

For all his bluffness, there can be little doubt Leigh’s work in both theatre and film reveals a commitment to social realism, self-effacement and an undeniable conscience. He is also in the unique position that, despite the varying fortunes of his films from the critical and international success of Secrets and Lies to the poor performance of the bigger budget (at £10m his most expensive to date) ensemble period drama Topsy-Turvy, he is still allowed to make the films he wants without being harassed by money men. ‘It’s because of the way I work,’ he explains, with the mumbled candour of a naughty schoolboy who has been getting away with something for far too long. ‘We don’t know how it’s going to be, we won’t discuss casting, they can either take it or leave it and very often they’ve left it and it hasn’t happened. You’ve only seen the ones that happened, it’s in the nature of the thing that protects me I suppose in a way. But I just want to go out there and make it up really.’

Despite his privileged position Leigh remains skeptical about the health of the British film industry: ‘I would love to be optimistic. There are a lot of very talented young people out there and people are still going to the cinema and there are still films to be made. And it’s good news that new technology means people can actually get their hands on equipment to make things cheaply. What’s not good news is that there is not enough support for people to make things uninhibitedly. People don’t trust people enough to go out there and take risks. I’m very lucky because all the work I’ve ever done has been made where I’ve been trusted to go off and just do it without committees forming.’

For now Leigh is busy promoting Happy-Go-Lucky which is soon to open in France (where Leigh’s films are adored) and has just been picked up by Miramax for US distribution. He refuses to talk about future projects until he has had a chance to approach a few people. As befits his character, he explains he is keeping everything ‘tucked away’ while continuing to be informed by a ‘pendulum of experiences.’

Happy-Go-Lucky is on general release from Fri 18 Apr. Mike Leigh on Mike Leigh (Faber) is published on Thu 17 Apr.