Siegfried, Royal Opera House, London

There are moments in the theatre that you just know you will never forget, and John Tomlinson's grizzled Wotan railing against the elements like Lear in the storm at the start of the final act of Siegfried is one. As he rides Stefanos Lazaridis's spinning airborne platform, hurling the last vestiges of his existence as a god, his books and his learning, to the four winds, Keith Warner's ever-intensifying Ring suddenly achieves an irreversible momentum.

Seeing and hearing Tomlinson lose his grip on godliness has to be one of the most gripping spectacles the operatic theatre has to offer. Wotan is suddenly an angry, bullying old man in a nightshirt, whose sole purpose is to finish what he began. His dismissal of Erda (excellent Jane Henschel), the earth-goddess mother of his child Brünnhilde, is a startling Warner moment. As he plunges his spear symbolically into her womb, the shock is intensified by the knowledge that this brutal act is one of terrible finality – an end to the way things were; a more hopeful beginning, perhaps.

That hope rests with our superhero, Siegfried, and it was always a neat conceit to have him grow up before our eyes. Warner has now developed this to take us from pram through adolescence to the hero's "entrance with bear" – a female chum in a bearsuit. Female? But Siegfried has never seen a woman... They might rethink that one.

John Treleaven has done a lot of work since last we saw him as Siegfried. His text is much sharper now, and though the "old school operatics" occasionally intrude, he sings with courage and stamina, landing most of the money notes without sounding like he's at the limit of his possibilities. When did you last hear a Siegfried who actually sang the top C in his entrance flourish?

Gerhard Siegel is, again, a tour de force as Mime, the boy's guardian and nemesis, spitting out words like chastisements, playing the clown while being the villain. But that clinching scene in the forest when he dons a rat mask to point up the duplicity between what he says and what he means, just doesn't work.

One niggle: why no flames as Siegfried scales the mountain to awaken Brünn-hilde? The orchestra (again magnificent) demands it at that point; the end of Die Walküre delivered it. Still, the literal wall between the would-be lovers is a striking visual metaphor, and even though Lisa Gasteen no longer has a top C, you can certainly buy into the sentiment of her line: "I was eternal. I am eternal."

In repertory to 31 October (020-7304 4000)