We theatre critics, paid to focus on the great fantasy world of theatre, know little of raw, real life. So for me Maria Aberg's brilliantly acted, in-yer-face and get-out-of-the-way promenade production of Roy Williams's Days of Significance, in which the audience mingles with actors on a stage of torn posters, barbed wire and a burger stall, comes as a shocking revelation of underclass turmoil.

Williams powerfully captures the fighting, feuding, foul-mouthed mood of Market Town Lads and ladettes on the Friday night booze, just before two of them depart for military service in Basra. Imitation vomit and urine on stage, and a drunk's apparently authentic penis lengthily flashed in front of mocking girls are tokens of a world of lost inhibitions.

This is Williams's urgent despatch from the New Asbo England and its rollicking inhabitants who make tabloid headlines. "We're going to get bladdered up, loved up, drugged up. Cos I want some dick. And I think you all know how angry and upset I can be, if I don't get no dick," warns Pippa Nixon's pugilistic Trish. She is, preposterously, an equivalent of Shakespeare's tart though not tarty Beatrice, since Williams's play is, written as a commissioned response - or perhaps retort - to Much Ado About Nothing.

Williams's interesting idea was to write about ordinary British squaddies caught up in Mr Blair's Iraq misadventure and reveal them as politically ignorant victims of war-fever who end up slaughtered or dishonoured. The points of similarity between Much Ado and Days of Significance are so slight they can virtually be discounted, even if Trish relishes a war of words with Jamie Davis's viciously belligerent Ben (Benedick), on the eve of his departure for Iraq where we observe him trapped and cowering in a Basra alley-way. His squaddie-mate, Jamie, whom Ashley Rolfe makes an impressive combination of vulnerability and bewilderment, takes the rap for atrocity and comes home to find his now enlightened girl, Claire-Louise Cordwell's sweetly enamoured and confused Hannah, in two minds about him.

Comic and shocking as social-realistic theatre, Days of Significance becomes a victim of its epic ambitions: Williams's essential plot about the exploitation of squaddies in Basra needs developing, with its romantic themes and redundant characters pruned. The production captivates by so vividly making us aware of today's exploited, angry and confused youth.

• Until 20 January. Information: 0870 609 1110.