It is strange that critical opinion should for so long have been so unforgiving to Mozart's La Clemenza di Tito - particularly as it is about clemency. Written to celebrate Leopold II's coronation as King of Bohemia, the opera was popular early in the 19th century, but has been taken up again only in the past 30 years. Welsh National Opera's 1997 production is one of those that has encouraged acceptance of the work.

In 1791 the imperial spin doctors were delighted with the choice of subject matter: Pietro Metastasio's allegory of the enlightened despot. In the face of jealousy, conspiracy, betrayal and murder, Titus laments: "If these are your friends, who needs enemies?" but forgives them all anyway. Glorious Titus/Leopold II.

Today the plot seems flimsy and Titus, a first-century AD Roman emperor, a bit flaky. Yet the great strength of this production is that the emotions and tensions of the characters are so acutely felt. Yannis Kokkos's staging and design have a simplicity of line that perfectly accords with the clarity of the musical conception.

Conductor Harry Bicket brought further clarity to the orchestral texture; the virtuosic clarinet and basset horn obbligati were high points. Timothy Robinson demonstrated that Titus is a title role to which tenors can honorably aspire, but few will have his noble bearing. Vitellia, conspirator and anti-heroine, was sung ably by Geraldine McGreevy, coming into her own towards the end when finally confronting her duplicity.

Mezzo Monica Groop was exceptional in the castrato role of Sextus. Her tone was rich and expressive and, in the aria Parto, parto, as finely articulated as the accompanying clarinet. Mozart's conviction that he and his librettist Mazzola had reduced Metastasio's original to a "real opera" was certainly borne out here.

· In rep until March 7. Box office: 029-2087 8889. Then tours to Oxford, Birmingham, Southampton and Liverpool.