Movies after September 11 were a lot like the five stages of grief. At first, nobody wanted to even mention the incident. The first I ever saw it remarked upon even obliquely was in Spider-Man, where an executive of Oscorp used the words 'after the bombing'.

Spike Lee was the first to refer to it directly, by having the character of Frank (Barry Pepper) live in an apartment overlooking the rubble of the World Trade Centre and say the line 'bin Laden can bomb next door, I ain't movin', in 25th Hour.

It was going to be a long time before anything to do with terrorism or radical Islam was treated with comedy (for the record, Fat Pizza was first in Australia, depicting an attack on an irritating, dark-skinned windscreen washer, bashed with his own squeegee and told 'that's for September 11'), but after nearly a decade, we have the first terrorist comedy.

If you want to look deep enough there's social commentary on how the people we label 'evil' and 'inhuman' are at times as disorganised, argumentative, egotistical and downright stupid as the rest of us. We meet four dedicated but talentless would-be radical British Muslim jihadi warriors and learn of their plans to strike a blow against the infidels.

Their story is a litany of failures. When Hassan and Waj go off to a terrorist training camp in remote Pakistan, they promptly blow up their own camp and are sent straight home. Omar has a dodgy car that can't be counted upon in the call to jihad. Fessal buys a truckload of bleach for explosives disguised as a woman with no inkling his beard might give him away. New recruit Ahmed is more interested in being a rapper, Waj is so stupid he thinks moving closer to the camera will make his toy AK-47 look bigger and Hassan (only marginally cleverer than the others) has to try and keep them all in check when they can't even agree on whom to bomb.

The mood is similar to that of the British classic In The Loop, with a strong sense of realism and a theatre of the absurd approach to how ridiculous people in general can be. Both elements combine to make sure the script is full of laughs, even though the broad working class UK accents get a little impenetrable at times.

It moves in a similar direction until the first shock that arises out of the comedy. After the gang have been running across town with backpacks full of explosive material in order to hide it, the sadsack-faced Fessal trips over a farm wall and blows himself up. The first blow in the jihad has been struck with the sacrifice of a martyr... and a sheep.

It's a violent turn that makes you wonder if you're still supposed to laugh. Even though it's raucously funny, writer/director Christopher Morris might be asking whether we're any more inhuman laughing at Muslim killers dying as they do when materialist westerners die at their hands.

The film slowly turns your hopes for the characters – a shift that may or may not be intended – and instead of being glad when such stupid, potentially destructive people are removed from he gene pool, you're hoping they see some sense. Especially as Hassan has a loving wife and an adoring son waiting for him at home, both of which seem to be inexplicably supportive of his quest for martyrdom.

When things really turn dangerous and the gang's boneheaded plans come to fruition, things turn more tense and you find yourself hoping nobody else gets killed. From then on the violence – made all the more shocking by official bungling by the police and authorities – feels more serious, but instead of telling you how to feel, the film just keeps delivering laughs and lets you decide.