The Wolf from the Door (Royal Court)

In between her pulverising Amanda Prynnein Private Lives last year and her upcoming appearance in the new series of Downton Abbey, Anna Chancellor fits in a posh terrorist, Lady Catherine, who is running wild with a beautiful young black boy, Leo (Calvin Demba), she's caught on a train.

My invocation of that Stephen Poliakoff television play is deliberate: Rory Mullarkey's free-spirited daub of a nationwide road trip is a Poliakoff-style fantasia of violence and revolution including, alas, the decapitation of a Tesco employee called Derek, the shooting of a policewoman, the stabbing of a choir master and the wholesale destruction of the Houses of Parliament.

Lady Catherine, to whom Leo offers a cupping of his left buttock followed by a full strip and sexual proposition (she declines), heads up an undercover insurgency peopled by church workers equipped with explosives and AK 47s, psychopathic Morris dancers and ladies who lynch; in case we hadn't noticed that Middle England was ripping itself apart, the scenes are punctuated by bursts of Elgar's Nimrod, Handel's Messiah and Holst's The Planets (Mars, naturally).

James Macdonald's unbuttoned, carefree production, designed by Tom Pye and lit by Peter Mumford, uses urban and country house projections in between two white pavilions, the auditorium strewn with bunting so that we might be sitting at an Alan Ayckbourn fête or Grange Park Opera.

The unlikely main duo is fortified by Sophie Russell and Pearce Quigley as everyone else, including the Bishop of Bath and Wells and his housekeeper (serving up a nine-bird roast with pizza starters) and a pair of gormless historical re-enactors dressed as helmeted Roundheads in a Little Chef. This bovine couple are on the receiving end of Lady Catherine's "big speech" about the necessity of synchronised destruction in an unfair society: "We are sleepwalking through our days."

She advocates the beautiful violence which brings change, the sort of manifesto not heard in Sloane Square for a long time, and all the more upsetting for being couched in so fresh and naively written a play. Whereas Lady Catherine's spur is political disillusionment, Leo is motivated by nothing more than hate for this country. Fair enough, I suppose, but his psychological conditioning is never explained; he's merely footloose, unattached, homeless and poor.

Mullarkey's writing veers between something you might find on the Court's Young Writers' Programme and his own quirky humorousness. He's a promising new talent. I particularly liked the rambling soliloquy of the dead-end mini-cab driver who, after muttering morosely for ten minutes, suddenly brightens: "Do either of you two keep up to date with the darts results?"