This seductive tragicomedy, which begins in an American mental asylum and ends in a double act of suicide and murder, strikes me with all the force of a theatrical hit.

There is no cruel laughter at the expense of the emotionally or mentally disturbed, as anyone who saw the film with Jack Nicholson will remember. Yet what insistent, persistent amusement the production achieves during the power battle between Frances Barber's authoritarian killjoy Nurse Ratched and Christian Slater's swaggering, anarchic troublemaker, whose mind is disturbed by nothing more dangerous than a wish for fun. This clash leads to catastrophe.

The production, vitalised by Terry Johnson and Tamara Harvey, arrives dramatically improved from the Edinburgh

Festival, where Hollywood's Christian Slater endured chickenpox-before opening night. Even in those tough circumstances there was no missing the way in which he and Barber hooked and held audience sympathies.

One Flew Over The Cuckoo's Nest, whose 1963 dramatisation by Dale Wasserman now seems rather crude, may be a bit dated in terms of how the mentally ill are treated. It does, though, stage a timeless struggle between the forces of authority and conformity and the Sixties hippie spirit of liberation and irresponsible fun.

For Slater's exuberant, small-time crook McMurphy, all dressed up in frayed jeans and irreverent attitude, the hospital serves as a convenient detour from prison. He arrives among the cowed, medicated patients, while Brendan Dempsey's apparently deaf and dumb Chief Bromden stands stranded in a crazy reverie from which he is rescued.

McMurphy excites them with ideas of gambling, basketball and evening TV. Sex will be provided for Mackenzie Crook's tormented, virginal Billy in the form of a willing girl smuggled in for an illicit party.

Miss Barber, who does not so much steal the show as annexe it, aptly plays Ratched as a victim of sexual repression, with Slater's attractive, taunting McMurphy her unacknowledged object of desire. Lips a lurid gash of red, uniform a dazzle of purified white, she radiates the smug, non-specific malice of the bureaucratic spoilsport whose main pleasure is inciting guilt.

Up against the force of her almost absolute authority Slater's McMurphy, who lacks Nicholson's cheek and charm, offers pugnaciousness instead.

The second act becomes a melodramatic battle of wills which McMurphy, emerging as a kind of Christ figure, betrayed by Billy, loses.

At the end Ratched stands by the bed of the lobotomised McMurphy and runs a hand over his brow. It is a gesture both sexual and exultant. The anarchist's absolute defeat mirrors the passing of Sixties dreams of hippiedom.

I confess I wept my way through the last 40 minutes.

Unforgettable.