As 'The Inbetweeners' leaps from sitcom to cinema, its makers are banking on the eternal appeal of juvenile humour

Taking flight: Simon Bird stars in 'The Inbetweeners Movie' (GETTY IMAGES)

Its scatological humour has won plaudits among a teenage demographic, while older viewers revel in its nostalgic take on their school days, a time when awkwardness around the opposite sex was as commonplace as outbreaks of acne.

Now, The Inbetweeners, the television series that follows four friends at the fictional Rudge Park Comprehensive, is transferring to the big screen. When The Inbetweeners Movie opens nationwide next Wednesday, the show's writers will run a gauntlet that many comedic brands have faced: Ali G, Kevin and Perry and Mr Bean tried to make the leap from TV to film and fell into the jaws of hungry critics. However, the makers of The Inbetweeners Movie are confident their characters' swansong has enough of an emotional punch to sustain interest for 90 minutes.

"It's got so much more of an emotional heart than the television series does," says Simon Bird, 26, who plays the know-it-all posh sixth-former Will. "The priority for a 23-minute sitcom has to be the jokes. The writers, Iain [Morris] and Damon [Beesley] had been sharp enough to realise that wouldn't work for a film. They needed something extra."

The "something extra" is a sense of "coming of age" for the teenagers – Will, Simon (Joe Thomas), Jay (James Buckley) and Neil (Blake Harrison) – who at the end of the film are expected to go their separate ways. That will be sad for both fans and cast, as those working on the show say it has been a familial experience.

Morris and Beesley met when they worked as producers on Channel 4's The 11 O'Clock Show. The first series of The Inbetweeners aired on E4 in May 2008 and then transferred to Channel 4 the following year. Ben Palmer, who has worked with Russell Brand and Leigh Francis, directed the film. He has been involved since the second series, in 2009.

The show has often been praised for its catch-all characterisation, which isn't subtle but which has thrust it into the mainstream. Will is high-minded but lacks common sense; Simon is romantic but hopeless at romance; Jay is a loudmouth and Neil is unintelligent but possesses sexual prowess that the others lack. Such clichés help to explain the TV show's appeal, which rests on teenage, regressive humour – jokes about sex and masturbation and frequent swearing make audiences laugh despite themselves.

Morris says he was drawn to teenagers because the demographic was well-covered in the US – shows like NBC's Freaks and Geeks capitalised on the humour that surrounds disjointed, sexually disenfranchised adolescence – but had not been tackled properly in Britain.

Conveniently, swearing teenagers provide an excuse for writers to plumb the depths: it is easier to laugh at teenagers making politically incorrect comments than to laugh at such things when voiced by an adult, who we all know should know better.

"I think there's a sense in which being a teenager means you say what you think might shock people," says Morris. "You want to see how far you can push things, and that is part of finding your own personality. You get a lot of leeway from your parents and society. That kind of freedom leads to terrible situations. You haven't got the benefit of experience. The other thing is that you think you know what you're doing, and that's fertile ground for comedy."

Bird, a president of Cambridge Footlights, is well-suited to playing a geeky character. At 26 he can pass for someone 10 years younger, and he comes from the David Mitchell school of comedy, in which a performer, while being marginally more cool in real life than the character they make their name playing, enjoys success based on the similarity between them.

"I don't think I'm as pretentious as Will is," Bird says. "And I hope I'm not as misguided..."

The film's high jinks have not eroded its right-thinking core. The Inbetweeners Movie stars the disabled actress Storme Toolis, playing a disabled role. This is relevant because of recent stories in the press about the director of the American series Glee, for example, favouring able-bodied actors in such roles because of what is claimed to be a lack of qualified professionals who are disabled.

"It strikes me as the new blacking up – let's call it 'cripping up'," wrote Toolis's mother, the children's rights campaigner Dea Birkett, in The Daily Telegraph this week. "From Tom Cruise in Born on the Fourth of July to the wheelchair dancer in Glee, non-disabled actors have grabbed all the good wheel-on parts."

"Storme did a brilliant job in the film," says Bird. "It would be odd to get an able-bodied actress to play that part when she could do it so well herself."

The Inbetweeners Movie' opens nationwide on Wednesday