Julius Caesar, Donmar Warehouse, London There are only two women - Portia and Calpurnia - in Julius Caesar and both of these wives have important things to say but find themselves sidelined. Otherwise, Shakespeare's account of the conspiracy to assassinate a dictator and the messy mistakes made in the power-vacuum left behind is an aggressively men-only affair. That's why the play is such a calculatedly provocative choice for the all-female cast in Phyllida Lloyd's intense and bracing revival Bunny Christie's design turns the Donmar into a prison gym: harsh strip-lighting, iron galleries; CCTV cameras. The inmates in their grey tracksuits are marched on and the conceit is that we are watching them rehearse their version of Shakespeare's tragedy. This framing device operates like a strange cross between Prisoner Cell Block H and the Marat/Sade as we see the politics of the prison impinge on the interpretation of the inner play. Impressively cocking a snook at the sceptics, Lloyd's fine cast - which includes Jenny Jules as a vehemently incisive Cassius and Cush Jumbo as a beautiful, dangerously charismatic Mark Antony - seem to be working on the principle of Ed Hall's all-male Propeller company: that the objective is to seize the essence of the character not to go in for any distracting impersonation of the opposite sex. Accordingly, the production is free to fluctuate between sequences where you are entirely lost in the story and moments that jerk you back to the reality of the rehearsal, as when the mob's murderous baiting of Cinna, the poet, gets wildly out of hand and the warders have to move in. The volatility of the crowd during the funeral orations and the sordid shifts of allegiance afterwards are conveyed with a restlessly choreographed edginess that underlines the inherent risk of putting on an anti-dictatorial drama in a jail. Of course, the overall concept can be used to justify certain simplifications. Instead of Shakespeare's more nuanced and equivocal Caesar, we get, for reasons I can't reveal, Frances Barber's butch, swaggering bully - a campily crude villain with an emphatic way of sharing his doughnuts. But it also allows for a potent doubleness in, say, Harriet Walter's wonderfully searching performance. You feel that she is both a haunted, hollow-cheeked, proto-Hamlet-like Brutus, racked by the contradictions of his political position, and an anguished, thoughtful inmate who, after this taste of imaginative freedom, understands the full philosophical bitterness of the return to incarceration.