The Romans In Britain, Crucible Theatre, Sheffield <!-- none onestar twostar fourstar fivestar -->

Mary Whitehouse may have assured Howard Brenton's 1980 play a permanent niche in legal and theatrical history when she launched a private prosecution against its director for "procuring an act of gross indecency" in the scene in which a Roman soldier attempts to sodomise a naked Druid. But by relegating it to the status of yesterday's cause célèbre, she robbed the piece of its right to be judged as political drama.

So, we should be grateful to Sam West, artistic director of the Crucible Theatre, for giving us the opportunity to reassess it. To vex Mrs Whitehouse's ghost, I would love to be able to declare that West's emotionally eloquent production reveals that the play - in which the Roman invasion of Britain in 54 BC, the British presence in Ireland in 1980, and the Saxon raids of 515AD are interwoven - is a neglected masterpiece of political theatre.

It establishes that the infamous anal rape scene is, in fact, one of the most morally powerful and pointed episodes in the piece. West stages it very shrewdly. The frustrated buggery takes place half-submerged in the deep pool that represents the river on Ralph Koltai's elemental set. This is a far from prudish adjustment. It allows the actors to make the violation look hideously realistic and it means the audience is not distracted from the human import of the scene by prurient technical curiosity.

The horror is heightened by the heartless flippancy of the Roman squaddies, who call the natives "wogs" and treat them as playthings. The assault was derided in 1980 as too crude a symbol of imperial conquest, but now it calls to mind those disgusting photographs from Abu Ghraib.

Given our involvement in the botched occupation of Iraq, we need a play that subjects the imperialistic impulse to intelligent analysis. But The Romans in Britain does not fit the bill. The idea that the Roman invasion created in our Celtic forebears an emulous imperialist mentality later exhibited in Northern Ireland is urged by the structure and by the coup de théâtre of having Caesar's troops rematerialise in combat fatigues as British soldiers in a savage segueing from ancient to modern.

But the figure who is supposed to connect the three worlds - an undercover English Army officer who performs a kind of suicidal act of contrition - proves to be the weakest link. And there are double standards. Where pre-invasion Celtic society is depicted as itself brutal and xenophobic, the division between oppressor and retaliating victim becomes much more clear-cut in the scenes set in 20th-century Ireland.

The production has the measure of the play's agitprop indignation but you end up feeling battered rather than enlightened.

To 25 February (0114-249 6000). A version of this review has appeared in some editions of the paper