Connolly and Terfel stand out in a thought-provoking Walküre at Covent Garden

If you've been brought up with the Judaeo-Christian ideal of an all-powerful, all-good God, Norse mythology can come as a bit of a shock. Wotan, the father of the gods, is philandering, deceitful, power-hungry, sentimental, violent and ultimately weak - the gamut of human frailties writ large. Combine all of those with a magic spear and the ability to control the weather and you know that things aren't going to end well.

The emotional core of Wagner's Die Walküre, and arguably that of the whole Ring Cycle, comes in the Act II dialogue between Wotan and his wife Fricka. The chickens of Wotan's duplicity are coming firmly home to roost, and Fricka forces him to abandon all of his self-delusions and decree the death of his illegitimate but much-beloved children, the Wälsung twins Siegmund and Sieglinde. The outstanding performance of this Covent Garden production (and there was plenty of competition) was Sarah Connolly's Fricka. It's often a thankless role of a shrewish wife - as an audience, we're clearly on the side of the noble Wälsungs against the loutish Hunding - but Connolly invested it with extraordinary depth of character, starting as the picture of wronged innocence simply trying to do what's right, then gradually showing ever steelier resolve while dismantling Wotan's deceits one by one with surgical precision. It was a magnificent and eye-opening piece of characterisation, all done within a context of top quality singing.

In that scene and his later reflective, tender scenes with Brünnhilde, Bryn Terfel's Wotan was equally compelling, depicting with complete credibility Wotan's mental contortions and range of emotions as he tries - and fails - to escape from the web of lies in which he has entangled himself. The Act II narrative in which Wotan relates to Brünnhilde the story of the Ring and his resulting predicament is very long, making this a punishingly difficult role, but Terfel did a wonderful job of telling the story musically; one's attention never flagged.

Director Keith Warner is principally concerned with the three key human relationships in Die Walküre: the incestuous love of Siegmund and Sieglinde, the antagonism between Wotan and Fricka and the father-daughter relationship between Wotan and Brünnhilde. He brings out top quality acting performances from all of the players, not least from Susan Bullock's Brünnhilde, who undergoes the opera's most convincing transformation as she changes from the light-hearted, fresh-faced warrior maiden into the beginnings of the figure of world-changing heroism that Brünnhilde will become later in the cycle.

All this is accompanied by some marvellous singing. Simon O'Neill brings lyricism and vocal beauty to Siegmund, as well as real thrill in those big moments when he demands the sword his father has promised and when he accepts the name that Sieglinde has given him. Sieglinde and Hunding are more one-dimensional roles, but Eva-Maria Westbroek and John Tomlinson (one of the great Wotans of yesteryear) did about as much as you can with them. And while some will find Bullock less memorable than some as Brünnhilde, the lengthy dialogue which closes the opera, in which she turns Wotan's fury back into the love of his favourite daughter, was a thing of real beauty; I enjoyed Bullock's lyricism and lack of stridency.

Stefanos Lazaridis's sets have come in for their fair share of criticism, but broadly speaking, I was quite happy with the sets for Acts I and II. There was plenty to look at - to the point of it all being a bit cluttered - but I thought the sets and several of the costumes were artistic and provided plenty of visual interest without getting in the way of the main agenda. Apart from the generally dark lighting (as ever, problematic if you're far from the stage), if the production has a weakness, it's in the less intimate, racier passages. Terfel was less convincing in his outbursts of anger than in his more reflective moments, and the famous "ride of the Valkyries" - in fact, more of a witches' sabbath as the eight Valkyries assemble on their mountain top - didn't really come off. Asking opera singers to do complex choreography and tricks with projected shadows may have been a little over-ambitious, and the movement on stage didn't give me the sense of excitement that is implicit in the music.

I find it a little hard to give an opinion on Pappano's conducting, because I was a long way up in the amphitheatre. All the singing voices projected up there with no problem - credit to the cast - but the orchestral sound didn't reach me with as much punch as I would have liked. I suspect this is simply a function of where I was sitting, because the whole thing knitted together smoothly, tempi felt natural and right, and there many good bits of individual playing, not least the driving bass and cello ostinati that start the opera. This was the sixth performance in the current Ring production, and it seems that Pappano has the whole engine purring smoothly.

This Ring Cycle is an expensive production which attracts an extremely knowledgeable audience - only real Wagner nuts would have spent both the money and the couple of hours on the web a year ago which were required to get tickets. If the interval and post-show eavesdropping is any guide, its audience came out thrilled and thoroughly satisfied with what they had seen.