THEATRE / Coal comfort: Paul Taylor on a coalmining drama at the Bush; plus My Mad Grandad in Oldham

Winding up Sandy is part of the friggin' training doon here,' comments one of the Scottish miners in The Cut, now transferred to the Bush. He's being unduly modest, though, for mutual provocation on a round-the-clock basis would seem to be the main industry in this pit, 3,000 feet underground, that forms the hermetic setting for Mike Cullen's play.

The writer was himself a miner for eight years, an experience which has left him dissatisfied with the 'unrealistic romanticised picture' you get in a lot of drama of miners as a brotherhood, united in the struggle for betterment in their communities. As a caustic corrective to this sanitised image, Cullen's gritty, foul-mouthed, tightly plotted slab of naturalism succeeds almost to a fault.

The convoluted power struggles on which Martin McCardie's production focuses with a thriller-like pace and intensity are set writhing by the return to the mine of Salter (Frank Gallagher), who has just served an eight-year sentence for a murder on the picket line that he did not commit. This one-time union demagogue has another death on his mind now, for shortly before Salter was released, his father, a pit under-manager, was mangled by a conveyor belt in an 'accident' that looked like the result of his own reprehensible negligence.

Determined to restore his father's reputation, Salter must try to manoeuvre or prise the truth from a trio of colleagues through whom Cullen provides a little cross-section of mining life as the pit moves into privatisation eight years on from the strike. An imminent tour of inspection by the general manager and board of directors (the 'tourists') tensely multiplies the possibilities of blackmail. Indeed, the plot has so many Byzantine twists that a knot of critics was seen forming an anxious self-help group in the bar during the interval. Through the hail of detail, though, you gradually discern the shape of a classical tragedy, for Cullen has given Salter, the compunctuous son, a psychologically vested interest in searching not for the truth, but for his own guilt-assuaging version of it. And in Hessel (the excellent Kenneth Glenaan), he has also equipped him with a transfixingly devious Iago-figure, a double-crossing weasel who pretends to be everyone's ally only to further his own promotion prospects.

The Cut reminds you, in certain respects, of Ma Rainey's Black Bottom, the August Wilson play that shows black Twenties musicians taking out their frustrations on each other rather than on the white recording industry that exploits them. Here, it's worse: we see a world where solidarity is vanishing and where unprincipled self-interest of the Hessel variety grotesquely apes the worst depredations of management. By the end, you feel that, in an odd way, Hessel is the most tragic character, tragic in not realising - as the conscientious, supplanted under-manager McGee (Jim Twaddale) profoundly does - that, in winning, he has inherited a moral hell where people, forced to live like animals, come to think like them.

The admirable script is full of acrid sarcasm and reeking tough talk, delivered with curt relish by the fine cast. Verbal threats, for example, don't come more picturesque than this: 'If you do anything to Sandy, I'll shove your head so far up your arse, it will look as though nothing's happened.'

The Bush, London W12 (081- 743 3388)