When Penny Woolcock was pushed to the ground and kicked repeatedly in the head by a young Afro-Caribbean mugger on the late-night streets of North London, she had a three-part epiphany. “Who are you?” thought the 59-year-old film-maker as she stared into the eyes of her young assailant. “What happened to you that you think it’s all right to do this?” she wondered, as she listened to the “horrible crunching sounds” from within her weakening skull. And finally, as the mugger fled and she vomited and slipped in and out of consciousness, she decided: “This would make a great film!”

Flash forward nearly three years, and the result of Woolcock’s epiphany is the gritty hip-hop musical 1 Day. The film, set in Birmingham using non-professional actors, local rappers and gang members, is a noir-inspired tale built around a sympathetic drug-dealer called Flash (Dylan Duffus). He has one rap-filled day (characters spontaneously break into rhyme) to repay £500,000 to a ruthless gang boss, to placate the demands of his three angry “baby-mothers” (mothers of his children) and to deal with his own morbid reflections — and all in time for a bullet-ridden finale. It is ambitious material, only occasionally undone by the sporadic inadequacies of the non-professional cast.

But the very idea of 1 Day, typically, has inspired outraged political pontificators, such as Chris Huhne and David Davis, to decry the National Lottery (which partially funded the project) for pumping £380,000 into a film about gang bangers, featuring gang bangers. Woolcock is unimpressed. “What is the lottery film money for if not to reflect something of the country we live in?” she says, tucked into the corner of a London restaurant, in jeans, rainbow-coloured top and rusty-red hair.

She describes how she began approaching street gangs in Birmingham. “They often thought that I was with the police,” she says. Eventually she was accepted by the charismatic Duffus, the son of a photographer. She held group meetings and discussions, and filled countless notebooks with observations and insights that became the working screenplay. On set, she says, she was indomitable in the face of her streetwise cast. “I was quite ferocious about people turning up on time, being prepared and being committed.”

The finished film, despite its sui generis status, is a recognisable Woolcock product. Like her Bafta-nominated Tina Goes Shopping (shot on a Sheffield council estate), her TV Shakespeare Macbeth on the Estate, with Ray Winstone, and the more recent Bradford-set Mischief Night, she is yet again exploring life on the tougher margins of society. When pushed, she warns that she doesn’t want to get too Freudian about this, but then adds that she “grew up in a very upper-middle-class British community in Argentina, but broke away from that at 18, and within six months of leaving my posh school was having a baby by myself in Barcelona, without any money” .

Her father was an accountant for Unilever in Buenos Aires, and after an entire childhood spent in a “crippling, stifling” British enclave she fell in love with the director of a radical, and illegal, left-wing theatre group. She fled to Spain with her man, leaving everything behind, including financial security and comfort. “Whatever it is that makes me make these films must have been the same voice that said, ‘I must be with this man!’ ” she says. “There must be some connection.”

The relationship ended when Woolcock’s child, a son called Dylan, was 1. She fled to England, where she was frequently homeless and even shoeless — “There was an entire summer in England when I didn’t even own any shoes.” She eventually found her metier in 1986 and made a film about punks while working with teenagers on a youth training scheme. From then on, and with some initial funding from Channel 4, her career took flight (she never married but, she notes wryly, has had plenty of “disastrous relationships”).

In recent years she has diversified into opera, making a film version of John Adams’s The Death of Klinghoffer, and directing the same composer’s Doctor Atomic on the New York and London stages (her next project is Bizet’s The Pearl Fishers for English National Opera). She says that she is fascinated by opera, but that film is her first love. And although she will soon be 60, she proudly retains that recalcitrant air that led her out of Argentina and still 1informs her uncompromising streak today – she’s currently working on both a sequel to 1 Day and an original idea about an opera singer who falls for a rapper. “If you were adventurous and slightly rebellious when you were 16,” she says, “you’ll probably be like that when you’re 60. It’s a depressing thought, but also quite encouraging.”

1 Day is playing at the London Film Festival on Oct 21, 23 and 24 (www.bfi.org.uk/lff), and is released on Nov 6

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