Written and directed by Andrea Arnold

164 minutes, rated MA 15+

How can a movie be so irritating and so good? It’s far too long and self-conscious, full of people I’d not want to meet and it appears to have been sponsored by American Big Tobacco, the teenage division. But durnit if this doesn’t get under your skin and take you to a place that’s fresh, albeit in a stinky, sweaty kind of way.

Andrea Arnold has made some powerful movies – before this came Red Road, Fish Tank and an admittedly mannered version of Wuthering Heights, where Heathcliff was black. When an English director makes an American road movie, there is always a temptation to preach about the horrors of American culture, or lack of it. You can find that here too but you have to dig. Arnold has subsumed her judgments so deep in an observational style that it’s easy to ignore that the film offers a harsh picture of American capitalism, the loss of innocence among the country’s youth and the despair that grips the have-nots.

That’s because these kids seem to having a lot of fun. Crammed into a mini-bus blaring with tunes, chugging bongs and singing at the top of their voices, they could pass for teenagers embracing a burst of freedom. The reality is more complicated: they’re selling magazine subscriptions door to door, every day a new territory, every house a new lie. The pressure is on. The queen bee is a smouldering Southern sex kitten named Krystal, who walks around in a confederate bikini when the team arrives at whatever nasty motel she picks each night. She’s the only one who gets her own room and doesn’t travel in the bus.

Krystal (Riley Keough, the grand-daughter of Elvis Presley, in a career-making performance) has a ruthless approach to every market. These people are poor, she’ll say as they drive up to a neighbourhood, just like you, so it should be easy to bleed ‘em.  Pity it’s not her movie, because she’s the most interesting character.

Instead, we follow 18-year-old Star (Sasha Lane), a young woman who knows that life is not where she’s at, looking after someone else’s babies, being groped by a no-hoper boyfriend in a hick town. She sees the gang of merry pranksters in a car park. She’s attracted by the charismatic Jake (Shia LaBeouf), even if he does have a plaited rat’s tail down his back. She dumps the kids and takes off with the caravan of misfits. They’re all sorts: the handsome surfie Corey (McCaul Lombardi) who flashes his penis at every opportunity; the introverted Pagan (Arielle Homes) who might just be insane; soulful Billy (Chad Cox) with his guitar, and so on. Not one of them is undamaged.

Much of the film is inside the bus, with a pounding soundtrack of recent indie hits across a range of styles. Everyone sings, in between lighting cones and swigging Jack. For teenagers, these kids hit the juice like there’s no tomorrow – which is perhaps the point. There isn’t. They’re all lost and broken; this bus is the only community they have – until Krystal fires one or more of them for not making the sales figures. Welcome to the family – now sell.

The developing romance between Star and Jake is like watching a car crash. She’s too young to see how dangerous he is, or she doesn’t care.  He appears to be Krystal’s slave, but Star wants him anyway. She’s an odd combination of worldliness and youth: seen too much but not enough to protect herself.

The characterisation keeps the movie going, even at this ridiculous length. In fact, the second half comes home so strongly that I forgot how long that first half took to become interesting. It’s the kind of film that rewards patience; it needs time to do its work. In the end, it becomes quite beautiful and sad. The world for these kids is harsh, but they don’t expect it to be anything else. Their disappointments came before we met them, and will continue after.  In between, Andrea Arnold takes us into the moment, while they try to have some fun, conning their fellow Americans.