It opens in 1879, in an unspecified part of Africa. Here, under a flapping Union Jack, a colonial administrator, Clive (Tim McInnerny, in minor John Cleese mode) tries to protect his household from the threat of the "natives" and their own lively sexual impulses. Churchill's innovation, which would be effective in a sketch but grows tiresome across a full- length play, was to swap male with female, black with white, and adult with child. A fluttery Dominic West plays Clive's wife, Betty. A wide- eyed Janine Duvitski plays Clive's young son, Edward. A pale, cadaverous Stephen Noonan plays the rebellious black servant, Joshua.
Churchill also moves the action forward 100 years in the second act (though the characters age only 25 years). So each actor plays someone else and the sexual politics are radically different. It might sound playful and interesting, but despite engaging performances - especially from Marion Bailey, who brings much needed depth to three roles - the characters remain as ciphers.
It's obvious why. Cloud Nine, which was premiered by Joint Stock in 1979, arose (in a very late-Seventies way) out of workshops, group research and discussions, impros, games, role reversals, people sharing experiences, reading books and talking "to other people". Then Churchill went away and wrote it.
Cloud Nine looks as if it was devised by a committee. Something needs to be said, and here are scenes devised to say it. If only a subject as complex and morally fraught as the Empire were reducible to these rehearsal-room building blocks.
Relationships come over as absurdly forced. If you had been sent the dramatis personae, along with instructions about the socio-political points that need to be made, you could work out yourself who needs to have sex with whom. At no moment - and this must matter for a classic - do you sense that the characters make the discoveries for themselves. No doubt the attack on pompous Victorian colonial patriarchs is absolutely justified. But in the way it treats people that it isn't interested in, Cloud Nine is not without its own brand of condescension.
That thoroughly modern celebrity, Oscar Wilde, suits our current taste for victims: he is as famous for his downfall as he was for his talent. The two sides of Wilde's fame are well interwoven in The Importance of Being Oscar, subtitled, in a way that catches the grandiloquent manner of the presentation, "The Wit, Triumph and Tragedy of Oscar Wilde". This was originally a one-man show put together by Michel Macliammir, a Willesden- born actor who decided to become deeply Irish. When Macliammir, who toured this show from 1960 to his death in 1978, was in Belfast in 1969, his dresser was the student Simon Callow. This week Callow revives it at the Savoy.
Unlike his Dickens readings on TV over Christmas (with his fluffy beard that bobbed up and down), Callow makes little attempt at impersonation. He appears, on Christopher Woods's set of receding gilt frames with cream chairs and tables, in a purple three-piece suit and open-necked shirt. With his silvery hair, lantern-jaw and trimmed beard, he has acquired a certain quixotic dignity. He's actorly, of course: he presses his fingertips together, nonchalantly swings his foot, and slows up and spaces out words at the end of one sentence, before rushing headlong into the next one.
Some of the details from Wilde's life are as familiar as jokes from the plays: the misspelt card the Marquess of Queensberry leaves at Wilde's club, the pathetic scene where Wilde stands on the platform of Clapham Junction and receives abuse from other passengers. Callow's performance is at its most inter- esting when sketching the more marginal figures (such as the Belfast prison warder who questions Wilde about literature) or in the later superbly sustained passages from De Profundis and The Ballad of Reading Gaol. He leaves you feeling Wilde's final infatuation was with sorrow itself.
Yasmina Reza's play Art (translated by Christopher Hampton) won two awards for Best Comedy of last year, presumably because no matter how astute and painful a play is, if there are too many laughs, it has to be a comedy. Seeing it this week with a new cast, Art allays any fears that this had simply been a boulevard showcase for Albert Finney, Tom Courtenay and Ken Stott. The only famous actor still involved is the producer, Sean Connery. Perhaps he has his eye on the Finney role in the movie.
The new cast doesn't bring the stately glamour - or the same hefty implacability - as the original three, so the tensions take longer to boil over. This has advantage: by the end, this Art is nearly as funny and slightly more moving.
The bearded, round-faced David Haig is not as choleric and intimidating as Finney, less obviously in need of homeopathy to control his temper. Anton Lesser is very effective in the Courtenay role, bringing a wiry, feral intel- ligence to Serge (one day he should play David Hare). Mark Williams has a lovely goofiness and can deliver a punchline with perfect stillness. Only the big set-piece about the wedding-invitation slips out of his grasp.
Nominally, Art is about art, but it's really about the way friends limit, control and mould one another. In the debate about whether Reza is either for or against the white painting that Serge has bought for FF 200,000, critics have (ironically enough) taken exactly the literal approach to Art that Marc takes towards the painting. It means this, it means that! But the pleasure of Reza's play lies in the highly skilled manner in which she reveals the process by which a friendship unpicks itself. The shifts in mood, the sudden interruptions, and the quiet regroupings, are beautifully handled by director Matthew Warchus.
There's a piece of loveable nonsense at the King's Head, Islington, where director Phillip George has collected a string of revue songs that brings together material by Sandy Wilson, Julian Slade, Peter Cook and others. JFK, it transpires, wasnot the only casualty of 1963: where were you when revue died? Much Revue About Nothing has a dotty end-of-term feel, with charmingly superfluous costume changes, sight gags and simple scenery flashing by. We speed through a period world of stripey blazers, boaters, furled umbrellas and spring in Fairbanks (fake snow and the appearance of a bear). Just when you think, those were the days, along comes a Cook number, "Laughing Grains", which mocks people who think those-were-the- days. The cast - Susie Blake, Jacqueline Charlesworth, Tony Whittle and Cameron Blakely - are all good. It's not uncommon to note that the audience roared with laughter. Here, you couldn't help noticing critics doing the same.
'Cloud Nine': Old Vic, SE1 (0171 928 7616), in rep to 26 Apr. 'Oscar': Savoy, WC2 (0171 836 8888), to 10 May. 'Art': Wyndhams, WC2 (0171 369 1736), to Oct. 'Revue': King's Head, N1 (0171 226 0364), to 13 Apr.