What, exactly, is the delicate balance in A Delicate Balance, Edward Albee’s strange and upsetting play that re-invented domestic comedy as bleak and mythical tragedy forty-five years ago?

Is it to be found in the mixture of that comedy with a nameless terror? Or is it the psychological equilibrium which eludes each character in turn, the surface of the pond never still as one stone after another is tossed in?

Albee remains best known for the earlier Who’s Afraid of Virginia Woolf?, but this play matches it in the dark existential night of the soul stakes over a dismal weekend in the Connecticut country house of Tobias and Agnes.

They are joined by Agnes’s alcoholic sister, Claire, then a couple of uninvited neighbours, Harry and Edna, who are too frightened to stay home, and their daughter Julia, in flight from another wrecked marriage, her fourth.

It’s fourteen years since Eileen Atkins and Maggie Smith played Agnes and Claire on the West End stage, so the very different, much darker, less bejewelled performances of Penelope Wilton and Imelda Staunton have no reason to suffer in comparison.

Wilton plays with infinite, suffocating patience and a velvety voice that turns Albee’s ornately compiled sentences into smiling boa constrictors, while Staunton combines Claire’s impossible drunkenness with a sense of physical danger; you feel she could explode at any moment, and you sigh with relief when she settles into the hilarious speech about trying to buy a topless swimsuit.

Albee once said the play is about people turning their backs on each other, but it’s also about the need for a cocoon in our lives. Tim Pigott-Smith’s amiable Tobias is haunted by his dismissal of a troublesome cat. Lucy Cohu’s volatile Julia finds her own room invaded by the neighbours, but is her long-term claim stronger than that of the instant demands for succour of Ian McElhinney’s placid Harry and Diana Hardcastle’s fragile Edna? Harry, after all, is Tobias’s best friend.

Director James Macdonald orchestrates the play with a chill sensitivity to its musical properties, and Laura Hopkins has designed a book-lined semi-circular living room that seems to mock its own solidity and cosiness. With the terror comes the plague. The headlights on the front lawn are the harbingers of doom. What else can we do, but drink and despair?