The American human-rights lawyer Clarence Darrow is one of liberal America's poster boys. David W Rintel's one-man biographical play of 1974 has been performed by Henry Fonda. But now that I've seen Kevin Spacey in the role, I don't much feel the need to see anyone else, not even the man from Twelve Angry Men.

In Thea Sharrock's superbly judged production, Spacey's gruff, rude and chivalrous Darrow stalks Old Vic's wonderful, in-the-round stage like a boxer waiting for his opponent. He makes forays into the audience which, in the best moments of a play that is otherwise sorely lacking in tension, turns sections of the crowd into juries. They sit slightly dumbstruck as Spacey projects his performance directly into their face.

Yes, the play is a vehicle that in lesser hands would feel like risk-free proselytising. But even though many of the arguments feel moribund, the sheer charisma with which they are delivered by Spacey is a thrill to watch.