If you gave Frank McGuinness's middle-class Irish characters English accents, settled them by the Sussex seaside with a period kitchen, and removed a modest sprinkling of expletives, then There Came A Gypsy Riding could easily be mistaken for an old-fashioned country house drama in Shaftesbury Avenue starring Ralph Richardson, Flora Robson and Margaret Rutherford. It would have opened in 1955 and run for just a few weeks.

For McGuinness's unenlightening play about suicide and bereavement is couched in a defunct theatrical form and lacks a dramatic pulse.

It dwells upon the grief and recriminations of the prosperous McKenna family, gathered at their west Ireland holiday home to mark the 21st birthday of their youngest offspring, Gene, who killed himself two years earlier.

Robert Jones's design slices open a modern house to reveal a sumptuous kitchen, an unvisited upper bedroom, exterior grey fields, granite pathways and a dead tree branch. It looks wintry but proves to be high summer. No wonder people complain about the heat, being overdressed in autumn clothes.

Lethargy creeps into Michael Attenborough's torpid production. Characters have an infuriating habit of delivering information to each other that they would know but we don't. "She's settled well back in college. Dominating the English department. He's recovered enough to keep expanding the (pub) empire," helpfully explains twentysomething Louise to her brother Simon of their parents, Margaret and Leo.

While these McKenna siblings have scarcely half a personality between them, the luminous Dame Eileen Atkins, as a distant cousin Bridget, who often sounds as if she has happily tripped out of her right mind, more than makes up for them. Indeed, without the humour of Dame Eileen's self-proclaimed "bride of Satan" or "confused fairy", There Came A Gypsy Riding would be even more of a dull theatrical trip than it is. "I found him, stretched out on the shore," she explains in the first detailing of Mark's demise. Her character remains inscrutable - cruel, canny or mental.

The arrival of Imelda Staunton's tense, grief-struck Margaret and Ian McElhinney's fine Leo does not precipitate any debate about the reasons for the suicide of the addictive Mark. McGuinness merely portrays people in bereavement's harsh grip. A freshly discovered suicide letter discloses next to nothing. Margaret, whose anguish is filtered all too self-consciously through Keats's When I Have Fears That I May Cease To Be, breaks down with poignant vehemence, though Staunton plays too much on one note.

It is the haunting Dame Eileen, all staring eyes and wild white wig, who half-saves the evening, by enabling shafts of black comedy to penetrate McGuinness's aimless gloom.