Long before Green Street was even in the can, photographs shot on location in London of the diminutive Lord of the Rings star Elijah Wood soaked in blood were raising concern. What was the LA-based Alexander saying about British football, which for years has been trying to escape the spectre of hooliganism? And what on earth was she doing to poor Frodo?
"The paparazzi took a lot of pictures and the only ones that were interesting to them were Elijah getting the shit kicked out of him," says Alexander. "People thought that I was making the most violent, bloody film in history."
Green Street is violent - it has to be in order to be convincing - but its violence has a point. Although initially we are meant to experience some of the adrenalin rush that Wood's disgraced Harvard student feels when he gets drawn into a gang of West Ham hooligans, and into his first fight, like him the film is ultimately repulsed by violence and its consequences.
Alexander refuses to demonise her characters. She knows their world intimately, and is fascinated by the ties that bind young men together, and the reasons why some find violence attractive. Yet, inevitably, the same question keeps arising: did we really need a film about football hooliganism? "No, we didn't," says Alexander, pugnaciously, "but I wanted to tell a story about young men and their need to do that male bonding thing, their need to stick together, and what a tribal thing does to you."
Alexander wants the Green Street gang to serve as a metaphor for other male groupings. When Charlie Hunnam's swaggering Pete Dunham tells Wood's Matt that they never abandon their mates in a fight, there are echoes, for instance, of the US Marines' code of never leaving a comrade behind.
Living in America, Alexander says, she has friends who are Marines, and when they talk about why they joined up, "you could put them next to the guys in my film and it will be the same thing." She adds: "A bunch of young men getting involved in a gang and football violence can equally be compared to a bunch of guys in Ohio signing up for a war they know nothing about, and being all, like," she punches the air, "'Yo, Marines! We're better than the army. We're better than the navy.' Then all together they go into Iraq and it's: 'We're better than the Hajees [Iraqis].' It's the same attitude."
The inspiration for the film was Alexander's personal journey with the City Boys. She became hooked on football aged five. At 15, she was teaching martial arts when two City Boys joined her class. Having bought into the "urban myth" about hooligans, she saw them as "honourable cowboys", and convinced them to let her into their crew.
For the next two years she hung out with them at pubs and matches, taking photographs of their inter-firm brawls but never actually joining in the fighting. "None of the guys wanted to fight a girl because you can only lose," she recalls. "If you beat her you're a dick; if you lose, you're even worse."
Alexander admits that at first she thought what she was witnessing was "really cool and really fun. I thought it was their way of choosing an extreme sport," she laughs, "and they were just adrenalin junkies." Like Matt, however, the film-maker gradually faced up to reality. She noticed that despite an unspoken law against hitting men when they were down, you could not rely on everyone to adhere to it. She found herself being called as a witness in trials and having to lie to save her friends, all the time worrying it would show up on her record. She saw, too, what happened when someone broke the gang's code of silence. Her illusions were finally shattered when around 40 City Boys set upon two members of a rival gang.
"It was too violent and too cruel," she says, ruefully. "As I was bringing it up with them, the same guys I had admired for so long turned round and said: 'Don't be such a girl. They deserved what they got.' So that was the turning point for me."
The men were not held together purely by violence, says Alexander; the emotional ties they forged were just as important. Most of them, Alexander included, were from families where one parent, usually the father, was absent or, like Matt's father in Green Street, emotionally unavailable. "So what happened is that when you joined this firm, you had these guys who, one day a week, were at the same pub, at the same time, every single week; it was more of a constant than any of us had in our home lives. There was a certain loyalty, a family-away-from-family that I think we were longing for."
The end of Green Street leaves Matt, the chants of his mates still ringing in his ears, carrying with him the confidence he has gained from being part of a gang but rejecting mindless violence. Even now, Alexander admits that she misses the camaraderie she found among the hooligans. "I always miss any kind of constant," she says, "especially now that I'm a film-maker who travels all the time. I'm always tempted to go to Catholic churches, although I despise the religion. But you want to go there just because it's the one thing in your life that's never changed. Personally, I'm not planning on having kids in the near future, because I think my job will always lend itself to breaking promises to somebody."
Now that she is filming her second feature, Life 'n' Lyrics, starring Ashley Walters (Bullet Boy), in London, Alexander plans to go to all the West Ham games this season. "That'll be good," she chirps, smiling brightly.
As we are about to leave, she reveals that she is hoping to do a film about religion in America. "I consider it to be my absolute baby more than Green Street," she says. "Religion is all good but we are almost back to medieval times now where we are obsessed with going into religious wars and electing our politicians based on their religious statements. It's all becoming very scary to me.
"I think I have a responsibility as a film-maker to bring not only controversial subject-matter to the screen but also to inspire a thought process. You can be Michael Moore and make Fahrenheit 9/11 but that's hitting people over the head, and a lot of Americans don't like to be hit over the head. I want to make films that make people walk out and say: 'Wow, I really question if this is all right.'"
Alexander expects to find herself in hot water. "Probably it will be the most controversial film ever," she says, chuckling. "I might as well pack my bags now and find a different home."
'Green Street' is released on 9 SeptemberReuse content