THEATRE / THE FRINGE: You've never had it so good: Sarah Hemming finds loss of innocence, a sense of betrayal and black comedy in David Edgar's Saigon Rose

THE party-goers wear flares and bemoan the decline of the Left, there are adverts for rebirthing classes in the newsagent's window and sex is conducted in the shadow of a virulent sexually transmitted disease. Saigon Rose is not a contemporary satire of Nineties mores, but an early David Edgar play set in 1975.

It's taken 17 years for Saigon Rose to arrive in London (now at the Orange Tree Room, Richmond, it was first staged at the Edinburgh Traverse in 1976) and it's an intriguing and entertaining document, reminding us that no matter what we see on the catwalks at the moment, the Seventies lacked taste. 'It's the reductio ad absurdum of the counter culture to a plate of fucking seaweed,' wails one character, faced with a green meal and greener tea in a health-food cafe.

Edgar handles his themes - loss of innocence and a sense of betrayal - in a bitty, playful style laced with black comedy. The 'Saigon Rose' of the title is a pernicious strain of gonorrhoea that unites four characters after their attempts to swing with the post-Sixties. 'It is such a ridiculous cliche to sleep with people and not know their name. People don't do that any more]' Clive rages when he discovers that his estranged wife has contracted the disease, and passed it on to him. He exacts his revenge by inviting her and their respective lovers to a gruesomely funny party where they are forced to eat humble pie. The characters' problems are familiar yet distant, their worries seem recognisable yet naive - this is after all an age where their common affliction can be treated with penicillin.

Rachel Kavanaugh's production is a delight, revelling in details down to the tight, flower-patched jeans and the virulently coloured Indian cotton smocks. She maintains the energy and light touch of the play and draws fine, funny performances from her cast, not least the criminally boring Clive (Michael Higgs) and his sweetly poisonous wife (Mairead Carty).

At the White Bear, Kennington, south-east London, they've also mounted a revival with flares. The Last Waltz opens in 1975, and likewise deals with innocence and betrayal, but here the characters are experiencing the Seventies from the closeted viewpoint of Army married quarters. Gillian Richmond's play (written in 1986) addresses the well- worn theme of friendship between misfits, but does so from an interesting angle, charting the relationship between two Army wives.

When we meet them, Christine is a wide-eyed new bride, while Denise is a brassy veteran, shockingly disloyal to the Army and her husband. But when Denise coaxes Christine to an Engelbert Humperdinck concert, a friendship is cemented. We dip into their relationship at intervals over the next 10 years, witnessing how it bolsters them against the insecurity of a nomadic life, until Christine's husband's promotion drives them apart.

Richmond's script is patchy - sometimes wooden, sometimes observant and lively - and the production matches this: after a nervy and rather creaky opening scene it eases into a believable story. Ineka Jones and Georgia Channon work too hard at their characters to begin with, but as they relax they draw you touchingly into their relationship.

David Mamet's latest play brings you into the Nineties with a harsh jolt. Now playing at the Orpheum Theatre, off-Broadway, Mamet's Oleanna will have its British premiere this June at the Royal Court, London (currently staging a fascinating season of tough new American writing), where it is likely to stir up as much passion as it has in New York.

In this provocative two-hander, a university lecturer tries to help a floundering student by telling her the truth, so undermining the rigid education structure within which she is struggling. But she, misinterpreting, or maybe choosing to misinterpret, his approach, reconstructs their encounter as attempted rape. Spotting his actual transgression (dismissing as bogus the education system which employs him), she frames him for a more obvious (though not committed) dereliction of duty. He, still assuming that his good intentions and Seventies liberalism will reach a young person, is crushed by her combination of political correctness and reactionary hard-headedness. So who is more patronising: him or her?

It's a brilliantly written play, Mamet illustrating on several levels how difficult it is to communicate, how language can betray you, how power can be shifted. The problem, given its inflammatory subject, is that the female character appears manipulative and is jerkily developed, while the lecturer is sympathetic: the American production has apparently sent spouses out locked in argument. The ambiguity of the ending is fascinating, however, and it will be interesting to see if Pinter, who directs in London, will bring even more nuances to the power shifts in the play. Book now to see it, but be prepared to take separate cabs home.

Finally, back in London, a quick mention of ATC's fine production of The Coaldust Affair, which runs to the end of this week in the Chelsea Centre, London. This is a slight, agreeable farce by Eugene Labiche about two friends who wake up after a drunken evening armed with all the evidence of having committed a murder. It is a disappointing piece in that Labiche, having set up their predicament, didn't quite seem to get round to working out a satisfying explanation for it. That said, the play is given a polished, boisterous and beautifully timed production by Jane Collins, with spot-on performances all round.

'Saigon Rose' runs to 10 April (081-940 3633); 'The Last Waltz' runs to 4 April (071-793 9193); 'The Coaldust Affair' runs to Saturday (071-352 1967). 'Oleanna' previews from 24 June and opens 30 June at the Royal Court (071- 730 1745).

(Photograph omitted)