The not-so-private life of Neil Bartlett

"WHAT IS your first memory?" "Who was your first snog with?" "What were family meals like when you were young?" "What were you like as a child?" Most of us don't want to be asked questions like these, let alone have the answers acted out by a group of people we don't know in front of hundreds of people we've never met.

But Neil Bartlett apparently does. On Tuesday night at the Lyric Hammersmith, the theatre's artistic director was the subject of Lifegame, an experimental improvisation on his own life. Lee Simpson, whose interview technique combines Jeremy Paxman's tenacity and Richard Briers's geniality, put these and other astonishingly personal questions to Bartlett. Simpson then directed his team of actors - all dressed, oddly, in varying shades of terracotta and sludge - to improvise a scene from Bartlett's answers.

Improbable have a reputation - and a wholly deserved one, it turns out - for the shock of the new. As Lifegame's deviser Keith Johnstone says in the programme, "If theatre did not exist then perhaps this would be a good place to start if we wanted to invent it from scratch." Lifegame's format engenders dizzying leaps between confession, memoir, impromptu acting and comedic improvisation. In trying to communicate just how invigorating an experience it is, you'll be hard pressed to avoid terrible thesp-speak cliches like "redefining theatre" and "pushing back the boundaries of performance."

It works best when it prompts the recovery of memory: as Simpson presses for more details, expressions of concentration, pain, joy and confusion shift across Bartlett's features. When, during the family-meal scene, the PE-teacher father demands of the eight-year-old Neil, "What's seven times seven?", you could see the adult Bartlett flinch and bite down on a clenched fist. Given his acting and directorial credits, it's hardly surprising that whenever Bartlett gets involved in a scene, the action rises to a new level. His is an extraordinarily still and controlled stage presence. Watching him as God, giving his 21-year-old self advice on handling his coming out to his parents, the other actors and the audience were transfixed - I don't think anyone in the auditorium moved a muscle throughout the whole scene.

There are a few downsides. We've all seen Whose Line Is It Anyway? The medium can give rise to in-gaffs that are, at times, inappropriate: as the Divinity teacher is about to make a pass at the young Neil, the actor mugs at the audience, panicked about an imaginary cup he is still holding: "I'll put the coffee down here then," he says, and everyone titters. And I don't know whose idea the musician was - would someone please confiscate his instruments? At every point he considered moving, he would give a little tinkly arpeggio on the piano, or twang at his triangle, making everyone jump and, in my case, want to be violently sick.

Lifegame taps into the deep desire in us all of wanting to be able to go back to speak to our former selves with the benefit of retrospect. And if, like me, you are insatiably nosey about people, the show is compulsive, voyeuristic viewing. But a game it certainly isn't - this is deadly serious stuff.