Mozart's La Clemenza di Tito was written to celebrate the coronation of the Habsburg emperor Leopold II as king of Bohemia in 1791. The date, two years after the French Revolution, is significant. Depicting a botched attempt to assassinate the Roman Emperor Titus, and his subsequent refusal to execute the conspirators, the opera examines the implications of the idea of benevolent autocracy and draws the conclusion that enlightened government necessitates absolute solitude and emotional isolation.

Two centuries on, the opera's politics can seem awkward and unreal. This production, by David McVicar for English National Opera, occasionally slides into confusion, though its merits as psychodrama are considerable.

McVicar's Tito, remarkably portrayed by Paul Nilon, is not quite Mozart's. In addition to being an idealist, he is also a martyr and a man kept apart from reality. We first encounter him as a Christ-like figure, dressed in Ecce Homo red and enduring a metaphorical agony in his palace garden. Later, as he decides upon the moral imperative of infinite forgiveness, he adopts cruciform postures, as power becomes his effective calvary.

We never see the world over which he rules. His subjects are kept off stage, while Yannis Thavoris's designs suggest closure and entrapment. Whirling janissaries hide their faces from him as he passes, as if he were an Ottoman potentate. Chinoiserie screens suggest that, like the emperors of ancient China, he must remain shut away from his people.

The religious-political symbolism sometimes feels overloaded; McVicar is more at home with the opera's complex erotics. Emma Bell's neurotic, terrifying Vitellia gets her kicks by dragging Sarah Connolly's driven, masochistic Sesto about by the hair. The relationship between Tito and Sesto is at once homoerotic and chaste, as they alternately cling to each other in desperation and break apart in confusion.

With the exception of Stephanie Marshall's shrill Annio, the singing is fabulous. Bell, thrilling from start to finish, gives the performance of a lifetime. Nilon - who, similarly, has done nothing better - is gracious, noble and moving, while Connolly, supremely at ease with all that tricky coloratura, combines emotional extremism with chilling restraint.

The conductor, making his ENO debut, is Roland Böer, kapellmeister at the Frankfurt Opera. In place of the stateliness favoured by some conductors, his interpretation is nervous, urgent and crackling with tension. Despite its flaws, this is one of ENO's finest achievements in recent years. You need to hear it.

· In rep until March 8. Box office: 020-7836-8300.