Arts: Not another severed ear ...

Any actor who has been into secondary schools with a theatre-in- education group will know that however high-minded the subject matter you quickly find a way of reinventing the material in a style that goes down well with the target audience. Otherwise (in my brief experience) fighting can break out at the back of the class.

Four Nights in Knaresborough is a first play by Paul Corcoran, a secondary school teacher for six years and also a copywriter. You might guess Corcoran was a copywriter from the pun in the title. The action takes place on four nights in a Yorkshire castle and concerns the four knights who take refuge there. You might guess Corcoran was a teacher from his handy knack of taking a remote event from 1171 and reinventing its feel as if it's a script that's just landed on the desk of a Soho film executive.

The event is the murder of Thomas a Beckett in Canterbury Cathedral. It's clear from the opening - the murder itself - that issues are going to be treated in a different manner from the poetic style favoured in Murder in the Cathedral. In T S Eliot's play one of the knights abuses the archbishop by calling him a "traitor confirmed in malfeasance": in Corcoran's play one of the knights abuses the archbishop by calling him a "f---wit".

It certainly blows the cobwebs off the history books. Twelfth-century violence is made accessible by looking very like 20-th century violence. We see four contract killers doing a nasty job for their client. It doesn't work out the way they planned it and they have to go into hiding. They don't know if their boss will disown them. Long before a severed ear is brandished round the baronial hall, and then chucked into the fire by its owner (on the grounds that "it's not much use to me now") the audience will find themselves thinking of Reservoir Dogs. This may turn out to be the ultimate prequel: Moat Dogs.

The director Richard Wilson gives Corcoran's wildly fluctuating script a solid straightforward production (imagine a crazy version of Ivanhoe on Saturday afternoon TV) that allows four strong actors to grab what credibility they can. They lust after the housekeeper Catherine (Mali Harries)and they lust after each other. Martin Marquez exudes a grim, brooding presence as the burly, troubled homosexual Reginald FitzUrse. Christopher Fulford instils William de Traci, a scholarly psychopath, with sinister efficiency, as he nips out one night to kill 18 local inhabitants, and - in a typical instance of Corcoran's flagrant anachronism - regales another Knaresborough civilian with his "CV". James Purefoy's Hugh de Morville stares mournfully into the paltry fire as he despairs of the violent bickering of his colleagues.

Johnny Lee Miller (Sick Boy in Trainspotting) has the most fun as the youngest knight, Richard le Bret, or Brito. He tries to hack open a loaf of bread with his sword and then kicks it in disgust into the fireplace with the explanation that he's making toast. When Catherine sits astride him on the table, in order to pull out his bad tooth with a large pair of pliers, the pleasure anaesthetises the pain.

It's all very peculiar. Corcoran's script is funny and daft, unbelievable and illuminating in equal measure. We go on a bumpy ride from playground abuse to theological debate. The central shift comes with the idea that immediately after the murder the madness and fury lie outside the castle as public opinion rages against the killers. A year later the madness and fury is a private one raging inside the minds of the four men. But black humour, macho rows and wacky tone, make this the most extreme example I've seen of an historical drama telling an audience more about the period in which it was written than the period in which it was set.

`Four Nights in Knaresborough': Tricycle, NW6 (0171 328 1000) to 4 Dec