THEATRE / No room at the inn in Thatcher's Britain: Thatcher's Children - Bristol Old Vic; Relative Values - Chichester; Antony and Cleopatra - Barbican; The Changeling - Barbican, Pit

AS ITS author predicted, London's reviewers have fallen like a ton of bricks on Trevor Griffiths's Thatcher's Children; but meanwhile their phones keep ringing with invitations to take part in broadcast debates on the show. The general idea seems to be that this is an unsatisfactory piece but an important event.

Well, the subject is important; and so is Andrew Hay's production, as an early result of the Arts Council's injection of enterprise capital into the regions through its 'Be Bold' scheme (a thoroughly Thatcherite initiative). Then there is the case of Griffiths himself - English drama's greatest lost leader since Osborne and our most politically literate playwright since Shaw: are there any signs of him emerging from the ideological wreckage and regaining his own voice? I thought so last year after The Gulf Between Us, his fractured but generously impassioned comment on the Gulf war. Now I am not so sure.

There have always been two writers inside Griffiths: the matchlessly articulate analyst of Comedians and The Party, and the class war cartoonist of Sam Sam. You may admire one more than the other, but you have to acknowledge both as honest. Another and more devious Griffiths then arrived in The Piano (1990), an adaptation of Platonov in which he vented his hatred of class privilege while taking shelter behind Chekhov. This Griffiths is the author of Thatcher's Children.

Based on 20 hours of video material shot by its excellent young multi-racial cast, the piece comes with documentary credentials. Whatever Griffiths does, in tracking the lives of seven Yorkshire children, the assumption is that he has the authority of factual evidence and personal contact. 'This isn't a propaganda play,' he has said; and he takes you off-guard in the charming opening scene of a primary school nativity play with one of the kings announcing 'I must follow the star as far as Leeds, me' and the innkeeper saying he has plenty of room. We then see them advancing into the gathering shadows. One turns to selling drugs, another to police corruption and baby-battering. A crusading reporter has her best stories censored and sinks to working for Sky. A Jamaican girl prospers as an accountant but then falls foul of Clause 28.

In no case does the play set up any pattern of cause or effect; and although the old friends sometimes meet, they mainly engage in confessional monologue. All that holds them together is Griffiths's editorialising: through the exhortations of a rock singer and screen projections of the 'Bad Lady' herself, who is presumably responsible for everything that happens to the characters along with the Chapletown riots, the battle of Orgreave and the Sabra-Chatila massacre. As it is all her fault, that means that the company remain blank innocents no matter what they do. 'I don't blame Wayne,' says the mother of the child he has killed: 'he was passed over for promotion.' In the end they return to the nativity play having learnt that there is no room at the inn; while Gurvinder (Kulvinder Ghir), enthroned in a virtual reality helmet, delivers Griffiths's verdict on England's past 20 years: 'This place is turning into shit.' This from the playwright who introduced Gramsci to the British stage.

At the opposite political extreme, Tim Luscombe's revival of Relative Values shows Noel Coward also shooting himself in the foot. In the words of its die-hard butler (Anthony Bate), this 1951 comedy celebrates the 'disintegration of the most unlikely dream that ever troubled the foolish heart of man - Social Equality]' What leads up to this rousing toast is the story of the Earl of Marshwood's engagement to a Hollywood star which comes unstuck when the dowager Countess's maid reveals herself as the star's sister. In the play's best scene, the family tries to cope with this emergency by rigging up the maid in one of her mistress's cast-offs and passing her off as one of themselves. Coward's purpose is to expose her hopeless ineligibility for such promotion. But, as gloriously played by Alison Fiske, the joke backfires; as she rams a bent cigarette down her corsage with the gruff demand, 'Peter, be an angel and get me a drink,' it is their manners and not hers that look ridiculous. Nothing else approaches the verve of this scene; but there is some decorative bitching between Susan Hampshire and Sarah Brightman, and a resourcefully funny performance from Edward Duke in the nothing role of the Countess's confidant.

Two Stratford productions, welcomed last year by my colleague Robert Butler, have moved confidently into the Barbican. Antony and Cleopatra has never become a director's toy; and in John Caird's production (played against Sue Blane's pharonic masonry with stately, barbaric music by Ilona Sekacz) its real requirements are fully met: expert stage management and wonderful acting. If there is a surprise, it is in John Nettles's Octavius, a warm-hearted ally nervously aware of his own limitations. Of the central partners, Richard Johnson is a rumbling giant periodically shrivelling into blustering guilt. Clare Higgins, at one moment prone at her master's feet while turning for a giggle with Charmian, has all the faces of Cleopatra and spins them like a colour wheel, before she rips off her wig and faces death with a close-cropped head. Making light of the play's cinematic battle scenes, this show fulfils Victor Hugo's ideal prescription for tragedy: magnitude and truth.

I hope one day to see Cheryl Campbell as Cleopatra. In the meanwhile she is giving a blazing performance as the murderous Beatrice-Joanna in Michael Attenborough's production of The Changeling. This role usually begins on a note of bashful virginity, offering the sadistic spectacle of purity defiled. That is not Campbell's way; from her opening scene with Alsemero (Michael Siberry) it is clear that her appetites are fully developed; and what follows is not so much a process of corruption as a gradual and hair- raising admission of her desire for the detested De Flores. Malcolm Storry plays him with a strawberry mark and the build of a butcher; and then contradicts your expectations with his modesty. It is another duet between coquettish freedom and insane devotion; like Antony and Cleopatra, they are made for each other.

'Thatcher's Children', Bristol Old Vic, 0272 250250. 'Relative Values', Chichester, 0243 781312. 'Antony and Cleopatra', Barbican, 071-638 8891. 'The Changeling', Barbican, Pit, 071-638 8891.