Simon Bird: 'Danger with The Inbetweeners is that it will no longer be believable that we are under the age of 30'

Simon Bird has just returned, suitably jet-lagged and reassuringly speccy, from promoting The Inbetweeners Movie in America. Already phenomenally successful in the UK, where it recorded the biggest ever opening weekend for a comedy film before going on to gross over ?45m, the E4 sitcom big-screen spinoff is now showing in 80 cinemas across the US. "They split us [the cast] up", says Bird. "I got San Francisco and LA – Blake [Harrison, who plays dim-witted Neil] got Columbus, Ohio. Actually the fact that it's in America at all is a massive bonus. It's not really designed for America."

That latter fact is reflected by the pallid MTV remake of the show, which has been likened to The Wonder Years rather than the raucous, potty-mouthed British original. Bird's next appearance on British TV will be in the second series of Friday Night Dinner, the sitcom about a north London Jewish family and their weekly Sabbath meal-time gatherings. Channel 4 rate the show so highly it has scheduled it to follow the new series of Homeland on Sunday evenings.

"Six more episodes of silliness and fun", promises Bird cheerfully. "There's no character development or growth". In the show, filmed in a real suburban semi in Mill Hill, a north London neighbourhood with a large Jewish community, Bird plays Adam, a twenty-something music-jingle writer who reverts to being a puerile teenager whenever he returns home to see his parents – straight-talking Jackie (Tamsin Greig) and eccentric Martin (Paul Ritter). In the meantime he fights with his younger brother, Jonny, an estate agent played by Tom Rosenthal, son of sports presenter Jim Rosenthal and the only actual Jew among the cast members.

"Robert [Popper] didn't set out to write a Jewish sitcom, he set out to write an autobiographical sitcom and his family just happened to be Jewish", says Bird, who was born into a solidly professional middle-class, gentile family in Guildford 28 years ago. Both his parents are academics, as is one brother. The other two brothers are doctors.

He read English literature at Cambridge, and became president of Footlights, where he met future fellow "Inbetweener" Joe Thomas (Simon Cooper), as well as Jonny Sweet. The trio went on to write and perform sketches at the Edinburgh Fringe – which is where Bird was discovered by Iain Morris, who was then casting his new E4 sitcom. "We decided to go and watch the Footlights", Morris recalled last year, "because, hatefully smug as those shows can often be, they invariably contain at least one or two brilliantly talented performers".

Bird's own estimation of his performing ability is more equivocal, and he has no trouble with critics who say that Adam from Friday Night Dinner and Will from The Inbetweeners are virtually indistinguishable.

"I don't really view myself as an actor", he says. "I'm under no illusions – I'm not Philip Seymour-Hoffman – but I think the other way is perfectly valid as well. Somebody I love is Michael Cera, who was in Arrested Development and Superbad, who I don't think is very different in the things that he's in, but he's always funny".

Bird's mother – an economics lecturer – would have preferred her son to have chosen a different career path. "When I finished filming the first series of The Inbetweeners she said: 'Good, Simon, you can go back to your PhD now'. My parents get annoyed when I imply in interviews that they weren't 100 per cent behind it, but I think that is a fair reflection. My mum came to the premier of the film, but I think she just finds it all a bit rude. They much prefer Friday Night Dinner."

But if Mr and Mrs Bird worried about their son settling down, they needn't have. This summer he married his girlfriend since university, Lisa Owens, who works in publishing, and he now has a mortgage on a house in London. Perhaps he wouldn't need a bank loan, I suggest, if there was to be a sequel to The Inbetweeners Movie – ?10m shared between the four cast members being one figure that has been reported.

"I know that Iain and Damon are talking about ideas for a sequel, but that's as far as it's gone", he says. "The two dangers are that it will no longer be believable that we are under the age of 30, and the other one is that we won't want to do it any more. The first film felt like a natural ending to The Inbetweeners, so I think as far as we're concerned we're happy to leave it there. We all really want to do other things."

One of those things – for Bird and Thomas at least – is Chickens, their First World War sitcom about three men (their old Footlights confrere, Sweet, makes up the trio) who, for one reason or another, are failing to do their duty on the Western Front. The pilot episode was aired last summer by Channel 4, but the full series – due out next year – will be on Sky. "Channel 4 turned it down", says Bird.

"We were surprised because it was very supportive throughout the whole thing and obviously Joe and I have a history of working for Channel 4. But I think that was probably the reason, in that Fresh Meat (which stars Thomas) and Friday Night Dinner are both on-going and The Inbetweeners is constantly being re-run, so it probably thought 'enough is enough'".

Chickens, he says, is more "terrifying" than previous projects because, instead of performing other people's material, this is their own baby. "Joe and I, having been in The Inbetweeners, have got this level of fame and recognition that we don't necessarily deserve", he says. "The Inbetweeners would have been a success with a totally different cast because the scripts are good – so while we were fortunate enough to be cast in it, we feel we still have a lot to prove. I guess this is our opportunity."

'Friday Night Dinner' returns on Sunday at 10pm on Channel 4