It is interesting that Welsh National Opera chose to illustrate its programme cover with an image of Tosca placing the Crucifix on Scarpia's body after stabbing him to death, thus highlighting this as a defining moment in the opera and suggesting, perhaps, that Tosca's hatred of the evil Chief of Police is greater even than her love for Cavaradossi. Certainly Deborah Riedel's portrayal of the eponymous heroine seems to support this view.

In the first act, I felt little of the passion that is supposed to exist between her and Rafael Rojas's Cavaradossi; she became a little more animated during the torture scene in Act II, and managed to show some real tenderness in Act III. But she seemed to reserve her greatest energy and emotional intensity for her scenes with Scarpia, which were some of the most compelling of the evening. Vocally, she was the strongest of the cast, singing with authority and commitment throughout, and demonstrating an extraordinary range of dynamics and tonal colour. Her Vissi d'arte was a high spot.

Rafael Rojas sang the beleaguered painter with great lyrical beauty, and his E lucevan le stelle was especially moving. But his voice seemed a little underpowered, and when duetting with Riedel was occasionally lost altogether. This added to the sense that there was little cohesion between the two. To be fair, though, he has just taken over the role from Dennis O'Neill, so perhaps a greater rapport will develop as the tour progresses.

Peter Sidhom also seemed a little underpowered in the role of Scarpia, and was not sufficiently menacing to be convincing. There was always a feeling that he wasn't giving it his all; the evil chuckle as he tormented Tosca wasn't quite hearty enough, his bearing not quite authoritative enough. This Scarpia was suitably cold and devious, but never succeeded in dominating the stage as he should.

Yet, despite these weaknesses, the evening was never less than totally captivating, as the opera moved inexorably to its fateful conclusion. Every time I see Tosca, I find myself wishing that the fake execution had worked, and that the opera could end with Tosca and Cavaradossi dancing off into the sunset. But such a fairy-tale ending would, of course, be at odds with the sense of foreboding that is present right from the start, when Angelotti staggers into the Church of Sant'Andre della Valle in search of refuge from Scarpia and his henchmen. Ashley Martin-Davis's claustrophobic sets which recreate actual locations and Mark Henderson's restrained lighting reinforce this feeling with great dramatic effect.

WNO's Oxford season continues tonight with Don Giovanni and tomorrow night with a new production of Tchaikovsky's Mazepa. Box office: 0870 607 7484.