A play with five writers was always likely to be a spoilt broth. This pool-written potage, apparently about ID cards, initially defies the proverb book. In time, though, it proves ill-structured and unsatisfying, admirable only while the plot is going nowhere.

The idea, part of the Court's 50th anniversary celebrations, comes from the early Seventies. Then the Court encouraged plays such as Portable Theatre's Lay By, written by David Hare, Howard Brenton, Stephen Poliakoff and others. This time the Court, trumpeting our current wealth of good women playwrights, put five of them into a room to see what came up.

What came up was the story of Claire (Tanya Moodie), a rare kind of image consultant who works by manipulating those consumer databases the anti-ID card lobby are so afraid of. She knows the effect a change of address has on a credit rating, or that your choice of toothpaste has on your marketing "type".

Around Claire, the writers work a series of riffs on the theme of identity. Ranting against ID cards, Maya, the teenage work-experience girl, sweetly played by the rather older Kathryn Drysdale, is hopeful that we are more than how others perceive us. Her hijabwearing friend Fatima, a non-religious sort who refers to other wearers as "fellow Ninjas", lends support to the hypothesis.

The counter-argument sees a gang of youths, complete with slightly hackneyed-sounding "street lingo", out to attain self-definition by committing crimes in front of CCTV cameras. Their eventual mugging of Claire is a piteous sight, and a revelation about her own past brings the first half to a moving close.

Then it's downhill. Strands of thought are twisted and abandoned as the play rushes madly to establish and resolve a plot. Claire breaks down: a reward for her efforts to control her own identity. It's a tidy tragic reversal, but coarse dramatic stitching makes it unconvincing. Arguments jump out of nowhere, inconsistencies crop up and the actors are lost emoting. When the ending appears like a fox in the road, the subtler drama and slowly constructed dialectic of the first half seem a distant memory.

• Until 22 December (020 7565 5000)