Mike Leigh's new film centres around Poppy, a free spirit whose openness and generosity make everyone around her fall in love with her. Miriam Craig talks to the writer-director ahead of his visit to East Finchley

"You don't have to laugh, I'll let you off," says Poppy, a primary school teacher played by Sally Hawkins in the film Happy-Go-Lucky, after doing her best to make a miserable shop assistant crack a smile.

She doesn't succeed, but the man's refusal to react to her breezy banter doesn't leave her any less chirpy. Whatever the situation - finding her bike has been stolen, a pupil at school being violent, a family spat - Poppy faces life with good humour.

Director Mike Leigh, who is a patron of the Phoenix Cinema in East Finchley, devised the film in his usual style, through improvisation and rehearsal with his actors, rather than beginning with a script. He says: "I started with a feeling - the feeling you get when you watch the film. The other thing I started with was wanting to make a film where Sally Hawkins would be the central character.

"I've worked with her a couple of times and she's extremely talented. I wanted to collaborate with her to create a special character."

Hawkins has already won the Silver Bear Award for best actress for the role at this year's Berlin Film Festival. Yet does Poppy's unfailing optimism mean she is an ideal who could never really exist?

Leigh says: "That may or may not be true, but she's not one of those people in a mindless blissful state, as though half her brains are missing, as though she's smoked a lot of dope. She's a grounded, responsible, fulfilled person.

"I don't think it's inevitable that in real life Poppy's optimism would fade. We all know people who are in their seventies or older where you think, They're still so positive', and there are other people who are 45 going on 106."

As we follow Poppy's life for a few weeks, we also come across a character who seems to be the exact opposite of her - her constantly angry driving instructor Scott, played by Eddie Marsan.

But the way this character clash is dealt with does not abide by Hollywood movie conventions; Poppy's deepest-held values are not challenged, and there is no moment of revelation that changes her forever.

Leigh explains: "It's not the kind of film where a character goes through a major, traumatic, life-changing experience. She's changing and growing all the time, because she's open and positive and learning. It's through an accumulation of experience that she changes."

Perhaps the change is in the outlook of the audience as they come under the spell of Poppy's infectious love of life. Leigh says: "In the end Poppy doesn't exist; she's a two-dimensional character on a flickering screen. The reality is how it resonates with your life, and that is, I hope, what the film does for people."

Leigh will answer questions from the audience after a showing of Happy-Go-Lucky at 7.30pm, at the Phoenix Cinema, in High Road, on Tuesday.

The event will raise money for the refurbishment of the cinema. Tickets cost £25 and are available from the box office on 020 8444 6789.