As is usual these days, Maureen Lipman is the best thing in a play whose cast includes Maureen Lipman. In Mary Chase's rarely revived, 1944 screwball comedy, Lipman is Veta, elder sister to Elwood (James Dreyfus) a wealthy bachelor whose life partner is a six foot invisible rabbit.

Chase wrote her Pulitzer Prize winning play - best known as the 1950 film version starring James Stewart - as a wartime morale booster. And its lesson, at least, is worth reviving: open your mind to the possibility of Harvey and you stand a chance of not only knowing yourself but important things in life, such as being kind and considerate. But although Lindsay Posner's production bowls along pleasingly, it can't hide the creakiness of this comedy.

Lipman's Veta - a widowed but lively social climber - is living with daughter Myrtle in the house bequeathed to her brother. But finding a suitor for Myrtle is no easy matter when your uncle is "the biggest screwball in town". For this reason, Veta attempts to get Elwood out of the way by having him sectioned in the local sanatorium.

However, what works best here is not the unravelling plot but the disintegration of Lipman's Veta. A buttoned-up control freak before her unfortunate misdiagnosis she reappears as a frazzled neurotic after her first taste of treatment - being stripped naked by a burley male porter and plunged into a cold bath.

It's a beautifully judged and often very funny portrait of injured pride. Dreyfus, meanwhile has the hardest job: filling James Stewart's shoes. He can't compete on terms of star wattage and charisma (who could?) but when his hard-drinking Elwood is at his most inebriated, Dreyfus does suggest a dark side that makes you wish he stayed drunker longer.

However, the play doesn't allow for such depths. Nor does it evoke sufficient laughs.