Fully Committed, Menier Chocolate Factory, London

At the sort of four-star, award-winning New York restaurant where mere mortals have to wait months to get within sniffing distance of a table, the phrase "fully committed" is a pretentious euphemism for "fully booked".

At the sort of four-star, award-winning New York restaurant where mere mortals have to wait months to get within sniffing distance of a table, the phrase "fully committed" is a pretentious euphemism for "fully booked". It carries the irritating implication that the eaterie is somehow performing a selfless public service rather than trading on the snobbish competitive instincts of would-be diners.

The entertaining trick in Becky Mode's play is to show us one of these swanky Upper East Side establishments entirely from the perspective of Sam, a harassed struggling actor who has a job working the phones in the restaurant's reservation department. The further twist is that both sides are brought to life in a vivid and virtuosic solo turn by Mark Setlock (who also helped the author in the development of the piece).

The grungy subterranean basement where Sam fields calls is, in every respect but the telephonic, a far cry from the wall-to-wall luxury above. As lowly intermediary, the character is well-placed to allow Mode to satirise the egomaniacal behaviour of both the restaurant big-wigs and the pushy clientele. Only a pathological optimist or one of the "people" of an A-list celebrity would dream of ringing in the hope of short-term satisfaction and the one guy among the hectic hubbub who can afford to sound confident throughout is an aide to Naomi Campbell. He's down the line several times, making ever more specific demands - from the dietary (she requires and all-vegan menu) to the theatrical (the bulbs in the lighting sconces are too harsh and will have to be replaced).

Other callers range from an 84-year-old lady with a rambling complaint about not getting her senior citizen's discount to an imperious society matron who finds that not even dropping the name of famed architect Philip Johnson can induce the restaurant to shift a visiting Sheikh from her preferred table. While trying to cope with these dissatisfied customers, Sam also has to deal with interventions from friends, family, and staff (the power-crazed chef has his own hotline to the basement via a special phone that keeps summoning beleaguered Sam with its peremptory farting sound).

Technically, the show is a tour de force. Mark Setlock seems to be grip of some madly exuberant identity crisis as he switches accents, mannerisms and personalities with dazzling speed. With three of four callers needing to be kept sweet simultaneously and put on and off hold, his exertions also give the pleasure you get from watching a highly skilled juggling act. As a piece of drama, though, Fully Committed is pretty lean cuisine. A woman at his agent's office tells Sam that perhaps he isn't getting roles because he tends to convey "a certain lack of entitlement".

The irony is that he has to listen all day to people whose sense of entitlement borders on the insane (at one point, a dowager demands to be placed in "first slot on the VIP Priority Waiting List"; Gordon Ramsay even puts in a brief appearance, making a characteristically fragrantly phrased request for a table). This theme, though, is never adequately developed and the plot (which involves a visit from the Zagats of the mighty Zagat Survey) is thin and tasteless. Reservations, then, onstage and off.

To 29 August (020-7907 7060)