Brendan at the Chelsea, Riverside Studios, London

Less than a century ago, the drunk was a figure of fun, fair game for comedians. Lately, television has brought us the spectacle of the disturbed personality as a source of horrified fascination for some, ridicule for others. Janet Behan's play about her uncle exists somewhere between these queasy-making forms. There are a few funny moments, but they are submerged in a sad, repetitious and distasteful portrait of the author as a dying man.

It is 1963 and Brendan Behan is in New York, staying at the Hotel Chelsea, presumably to dry out and write a book. But a bottle is stashed under the bed, and the last instalment his publisher received was blank. His wife, Beatrice, is on her way from Dublin, and his girlfriend, Suzanne, has sent him a photo of their baby.

The ingredients seem to promise a phantasmagoric comic-horror circus, but Brendan at the Chelsea does not deliver it. None of the loopy atmosphere of the Chelsea is evoked beyond a report that one of the snakes kept by a neighbour has escaped. The Chelsea girl we see most of is a dancer engaged as a minder called Lianne, who bustles about acting as a foil for Brendan's rages and fantasies. The character adds nothing of interest, and Eva Crompton, with her often inaudible voice, adds only confusion. Suzanne waits in the lobby but never appears.

As Brendan, Adrian Dunbar, who speaks in a rasping Dublin brogue, is frequently difficult to hear as well. He has been excommunicated, he tells us, but "you don't want to take dese t'ings pairsonally." He drinks, he shouts, he falls. He relives memories and has dreams, in one of which a transvestite dressed as Lauren Bacall gives him a blow job. He receives the adulation of gay men, whom he tells that an Irish homosexual is "a man who prefers women to drink". He goes to the theatre where his play The Hostage is on and clambers on to the stage singing.

All of this is shambolic. Dunbar's lack of energy in the lead role characterises his direction as well. The small cast seems lost on the wide stage, and the pace is slack, with no suspense – Brendan just drinks and drinks, and goes on acting reckless and ugly. We don't see the brilliant writer, the rebel, the generous spirit.

One performer shines through this tedious and painful show. As Brendan's wife, Brid Brennan personifies quiet, despairing love and touching dignity.

By dramatising the most regrettable aspects of Behan's life, by seeking our sympathy without showing him as sympathetic, Brendan at the Chelsea invites us to a love feast, but one at which the table is bare.