At first glance — and, indeed, at second and third — it looks exactly like that picture. You know, the one that David Cameron and Boris Johnson are anxious we shouldn’t see any more and try to forget all about. Indeed, the Prime Minister is said to be so keen to distance himself from his student antics in Oxford’s Bullingdon Club that he eschewed the traditional tailcoat when attending a pal’s wedding in Chipping Norton (where else?) at the weekend.

Laura Wade’s stonkingly good play Posh — newly arrived in the West End — does not mention ‘the Bullers’ by name in its hard-hitting, and at times extremely funny, exposé of the way she supposes the university’s financial and social elite conducts itself. We must conclude, though, that it has been her model — with a bit of the Assassins (remember them?) thrown in — for the Riot Club, whose hard-drinking, foul-talking, pub-trashing, oik-bashing antics she depicts.

“Little boys in the playground” is the verdict of one member of the group who comes to be disenchanted with its conduct. And, indeed, it is amusing to observe the juvenile incompetence with which their club dinner is arranged in a private room of the Bull’s Head Inn, an establishment — prop. the long-suffering Chris (Steffan Rhodri) —said to be sufficiently far out of Oxford to be unaware of the club’s reputation The task of deciding on the menu has been eagerly seized by Guy Bellingfield (Joshua McGuire), a thrusting ‘hack’ with an ambition to succeed the silkily smooth James Leighton-Masters (Tom Mison) as president, though he has a serious rival in Dimitri Mitropoulos (Henry Lloyd-Hughes), scion of a Greek ship-owning family. Guy’s culinary ideas, alas, do not find favour with his colleagues, though they do inspire some good jokes: “So how d’you make an Eton mess?” “Tell him he only got into Bristol?”

To George Balfour (Richard Goulding) has fallen the duty of supplying the cocaine. It turns out he has had a “bit of a problem with the old, um, procurement, actually”. The money was seized by a tramp in Blackbird Leys and when George couldn’t pay the dealer “he looked very cross and did some shouting and then I did some running away”.

Sex is the department of the wise-cracking swordsman (yes, he does fence) Harry Villiers (Max Bennett), who has hired a hooker for the night in the expectation she will pleasure the whole club from beneath the dining table. But business-like call-girl Charlie (Charlotte Lucas) arrives through the window (she is known in the bar) to announce: “I’m not going to do ten people in two hours. I don’t do more than two visits in a row without a proper break.”

Unsavoury aspects of the club’s activities are illustrated in the room-trashing that we hear has been inflicted on the two new recruits, ‘Magdalen Mary’ Miles Richards (Edward Killingback) and amusingly eager Ed Montgomery (Harry Lister Smith), and in the unspeakable punishment meted out to Toby Maitland (Jolyon Coy), bewigged in his shame, for the heinous crime of speaking about the club to the Press.

How the Riot Club’s much-vaunted notion of brotherhood turns out not to apply in practice is seen in its treatment of the most frighteningly right-wing member Alistair Ryle (Leo Bill). To discover what prompts this you must see this exceptionally entertaining, thought-provoking play. Expertly directed by Lyndsey Turner (and with a cappella musical numbers cheerily supplied by the highly talented cast), the Royal Court production of Posh is at the Duke of York’s Theatre, London, until August 4. Box office: 0844 871 7623, www.royalcourtatdukes.com