Honest, Queen's Head Pub, London

If each of us were to masturbate into the same cup, it would "produce more of worth to the British taxpayer" than the section of the civil service called the Strategic and Tactical Development Team (acronym STD. T) where Dave, a young Welshman living in London, has the misfortune to work. Nursing a Coke and an existential hangover and clad in a dark suit and tie, Dave – portrayed with a wonderfully nutty charm by Trystan Gravelle – makes us his captive audience in the panelled snug room of the Queen's Head pub in Denman Street near Piccadilly Circus. The epic futility of a bureaucracy effective only at sustaining its own pointless existence has made Dave come unhinged. As he points out, even the name of his department is an offence against reason – "strategic" and "tactical" cancelling each other out and "development" meaning anything you like.

The result is that he has gone on two simultaneous binges – one alcoholic, the other a reckless spree of truth-telling. The main section of this driven, scabrously funny monologue by D C Moore takes Dave on a booze-fuelled odyssey that begins at an office party in a night club off Regent St, where they play "80s music so tedious it could literally make your heart stop" and where he treats his pseudo-cool, vacant boss to the news that he's a useless "posh spastic". We then see nocturnal South London through his manically perceptive, bracingly reductive gaze. Trendy Clapham, he reports, is like an AGM comprised of every graduate who happened to be "the biggest fucking prick" of their year. Lobbing an opened can of lager at a group stood outside a pub, he reckons that "there's not a single moment of doubt between them – or honour."

The show packs more into its 40 minutes than many a two-hour marathon.

To 3 April (020 7478 0100)