THE CRITICS : Always look on the black side of life

In slickness and in health, Bill Cosby reigns serene. In more than 30 years as one of the top people in his field, the man who was Dr Huxtable had never got around to performing on this side of the Atlantic. When the time finally comes to make his London debut, he jets in without so much as a single sycophantic retainer in tow, has dinner with some friends, brings a dressed-up-to-the-11s Royal Albert Hall to its feet with two hours of elegantly crafted domestic discontentment, then meanders off home again without so much as a word to Richard and Judy.

Happily married and in the throes of a sumptuously well-provided-for early retirement, you might think Cosby would not have much to complain about, but that would be to miss an important point. It's complaining that has got him where he is today. So it's strange that so many people have expressed concern about his plans for an American version of One Foot in the Grave: it's the children in The Cosby Show who are nauseatingly cute - the old man can out-grump the best of them. And therein, strangely enough, lies Bill Cosby's political importance. In establishing that black Americans can have little problems as well as big ones, he has been a soft-shoe subversive rather than the social-climbing sell-out of critical imagining.

Watching Cosby on stage in this country for the first time, it is easy to see what made Richard Pryor admire him so much that (as Pryor confesses in his recent autobiography) he devoted the early years of his career to imitating him. The subject matter - driving disagreements, his family's love of fried food ("My father's heavily larded sperm hit my mother's heavily greased egg ...") - is as familiar as an old slipper, but the easy elegance of its delivery and desiccated cool of Cosby's endless rhetorical flourishes are unique.

It's not all good wholesome fun either. Cosby's celebration of intra- marital flatulence strays into realms where even Billy Connolly might fear to tread. And his piece de resistance is the longest and most graphic description of a prostate check-up ever attempted in a British theatre: the midst of a stool examination, apparently, is "the only time when black is not beautiful".

Down at the Riverside Studios' Channel 4 Sitcom Festival, the Cosby Shows of the future emerge blinking into the light. Or something like that. As an aesthetic innovation, the idea of putting three triple bills of would-be sitcoms on the stage seems problematic (what next - David Baddiel writing a novel?), but the results are intriguing. If only for the way they illuminate the subtle contrasts in theatre and sitcom's different forms of restriction.

When each of the first trio of comedy playlets runs over its allotted half-hour, there is a genuine sense of outrage (at least if destiny traps you into watching The Upper Hand, you know when it's going to finish). And the most authentically sitcom-type emotions of exquisite social embarrassment are generated not by anything that happens on stage, but by a baby in the audience gurgling at inappropriate moments.

Neither Marcy Kahan's agonising opener Kerouac (a female central character named after the author of On the Road? No stop it please, you're killing us) nor Patrick Barlow's workmanlike Game On-meets-The Flintstones finale Basic Instincts offers much hope for the future, but Tunde Babalola's In Exile seems to have what it takes. As Meat Loaf once sang, one out of three ain't bad. This harrowing saga of a deposed African dictator making a new life for himself in St John's Wood with only an ambitious personal assistant, a son who wants to be a dancer and a video of The Lion King for company achieves just the right balance of enclosure and escape.

Channel 4 Sitcom Festival: Riverside, W6 (0181 741 2255), Wed-Sat, to 27 Jul.