By the time The Riot Club opened on Friday, the voting in the Scottish referendum was over.

I've no doubt that anyone watching this fictional account of the infamous Bullingdon Club - the Oxford University society which has spawned Tory leaders including David Cameron, George Osborne and Boris Johnson - at an earlier date would have left the cinema thinking Yes, Yes, Yes.

Adapted by Laura Wade from her stage play Posh, it opens briefly in the 18th century. The 7th Earl of Carlisle is having sex with a woman in his Oxford chambers, when her cuckolded husband arrives and promptly runs him through with a sword. At a dinner, his university pals honour the man they knew as Lord Riot, bemoaning the fact that the debauched cad "expected to be Lord Chief Justice one day". They form a club in his name, with the intention of behaving badly for centuries to come.

In the present, a new intake of Oxford students falls into the haves and have-nots, privileged public schoolboys and ordinary youngsters who give a broader regional representation of the country. "What's a nice Westminster boy like you doing with all those boot-strapping regionals?" one incredulous toff asks Miles Richards (Max Irons), who is deigning to go out with Lauren (Holliday Grainger), a northerner with the notion that she's at Oxford to work for her degree.

The wheels are in motion to bring new blood into the Riot Club. When one fresher asks about the club, he's told: "If you've got to ask, you're not really the right sort of chap." Miles can't resist the lure of exclusivity and is inducted along with Alistair Ryle (Sam Claflin), a frightening individual who is at once scarred by and dangerously informed by his upbringing.

The physical humiliations for recruits are accompanied by the total destruction of their rooms, reflecting the club ethos that anything it destroys can be replaced if you're rich enough. "This is what they do to people they like," comments Lauren with horror; we're about to see what they do to people they don't like.

The centrepiece of the film is the club's annual dinner, in a country pub whose unsuspecting owner (Gordon Brown) can't help fawning over his well-to-do customers. His daughter Rachel (Jessica Brown Findlay) is more wary.

The club doesn't amount to much more than a well-dressed and extremely well-funded way to get drunk. The problem is that when their sense of entitlement is challenged - whether their 10-bird roast is a bird short, or the prostitute they've hired doesn't do orgies - these puerile young men react very badly indeed. And this time they are stoked towards violence.

While Wade covers the familiar ground of class war, her surprising suggestion is that whatever negative feelings the working class may have about the upper classes, it's nothing compared to the outright hatred felt by this younger generation of aristocrats. More pointedly, she opens our eyes to the fact that such individuals routinely go on to run the country.

On stage this must have been quite something; on screen, it feels a little one-dimensional and heavy-handed. Yet it packs an undeniable punch.

Director Lone Scherfig, a Dane who seems to enjoy British stories (An Education, the Glasgow-set Wilbur Wants to Kill Himself) draws strong performances from her young cast, not least the women, who represent the only laudable figures on display. Incidentally, Ben Schnetzer and Freddie Fox are also to be seen right now in Pride, as gay men supporting the miners. They're remarkable convincing on both sides of the class struggle.