this is where we got to when you came in, Bush Theatre, London

For nearly 40 years the Bush Theatre has been perched above a pub in west London: a small new writing venue with a huge reputation. More than 250 playwrights have had their work staged there. Now, as the theatre moves on to handsome new premises down the road, the final show bids farewell to the old building – but not, ironically, with a single new play. Rather, this is where we got to when you came in is a quirky backstage tour, staged by experimental group non zero one, in which the theatre itself is the show.

It’s ingenious, affectionate and poignant – and it plays mischievously to the nosy parker in each of us. Audience members explore the empty theatre in groups of four, given directions through loudspeakers, MP3 players and phones. We’re encouraged to pry, poke and pick things up. We mooch around the admin office, reading notes, flicking through boxes of personal belongings, each of them testament to a hectic lifestyle (artistic director Josie Rourke’s contains balsamic vinegar and hairspray). Our guide points out the busy road and the frequent sirens; on cue, a police car screams past – even the emergency vehicles have dramatic timing here.

We move on via the Ladies’ loo (compact) to the dressing room, where we enact a group drama exercise pretending to be actors asleep on the floor. Then it’s the writer’s room: a tiny white space in which we contemplate the liberty – and the terror – of the blank page. A script miraculously appears, writing itself on the white table (if only it were that easy). Everywhere voices from the theatre’s past – writers, directors, actors – reminisce, filling the space with friendly ghosts.

If you have ever been in the Bush audience, did you realise that the actors got to the stage via an external fire-escape (under umbrellas in the wet weather)? We trace their steps, pausing to survey the many cigarette butts below that speak of first-night nerves, and wait, skin tingling, behind the doors to the stage for a cue to enter. The auditorium is our final stop, now sadly empty, seats stripped out. It’s impossible not to be moved as you survey the small, scruffy space that has hosted so many stories.

This is a lovely note to go out on. It’s a droll, moving piece that allows each visitor to play many parts and, while celebrating the building’s history, reminds us that what makes a theatre is not so much the bricks and mortar as the industry and energy of the people in it.

bushtheatre.co.uk