Gotterdammerung, Royal Opera House, London

The final part of Wagner's Ring begins with the daughters of Erda, the three Norns, taking stock of unfolding events. It's their "previously in the Ring" moment. But for all their "eternal wisdom", they speculate but cannot be sure of the outcome. I now can.

Keith Warner's Royal Opera staging has developed and sharpened and grown mightier as a whole in ways that might not have been predicted when each part was first revealed to us. Even the naysayers must now surely acknowledge that Warner's ideas have coalesced into something bold and commanding.

The foundation of this Ring has been the extraordinary work of Antonio Pappano and his magnificent orchestra, whose gripping narrative has held us in thrall every step of the journey. For all the fine detail, Pappano has, like Warner, thought big. Together they have set off like Siegfried on his Rhine journey to "new adventures".

Has that sequence ever been more effectively staged than it is here? I don't think so. The mountaineering ropes (neat parallels here with the Norns' rope of destiny) tell us there are great heights to be scaled. And as one of Wotan's ravens provides our viewpoint for Siegfried's cinematic voyage of discovery, we, like him, glimpse the future.

Humankind arrive on the scene as Gibichung Hall is revealed. They gaze through the reflective glass windows at events unfolding inside. And it is here that designer Stefanos Lazaridis plays his design coup of the cycle. That glass-panelled interior is a chilling replica of the Tarnhelm, the magic helmet that Hagen will use in his plot to murder Siegfried and steal the Ring. We are effectively inside the Tarnhelm. We are also very much inside Hagen's head when Warner has him sit downstage watching his devilish plot unfold for the remainder of the first act.

Hagen is Kurt Rydl, black and booming of voice and oozing evil intent. He leaves us in no doubt that power is truly a sexual high for him. And, with a little help from Warner, his plan works like a charm. It's a brilliant idea to have Siegfried appear wearing the Tarnhelm and then have Gunther (the excellent Peter Coleman-Wright) simply emerge from behind him at the moment of transformation. So Siegfried, helmeted in the shadows, provides the disembodied voice for Gunther's form. So simple, so effective.

So, too, Wagner's hair-raising middle act where Hagen's thuggishly Teutonic vassals play rent-a-crowd for the arrival of Gunther and his reluctant bride-to-be Brünnhilde, symbolically encircled with barbed wire. In this chauvinistic world it is, of course, the women, suitably attired as serving-maids, who haul the wedding platform downstage. The gods are already history, immortalised in gold like outsized Oscar statuettes.

All our hopes, then, are on Siegfried's broad shoulders – but John Treleaven once again sounds stressed after his marathon in the previous opera. Even so, where his voice may desert him, his courage does not. And that's something he shares with Lisa Gasteen.

Gasteen's Brünnhilde has really grown since her first appearance in this Ring. She may not have a top C any more but her other notes are considerable and, more importantly, born of conviction. Wagner created one hell of a woman with this character and Gasteen gives us all of her – her pride, passion, hurt, scorn, and defiance, not least in the great scene with Mihoko Fujimura's sensational Waltraute.

And so it ends. Warner gives us everything that Wagner asks for come the final cataclysm. But significantly it is the youth of humankind that finally consigns the gods' statues to the flames and, as a gigantic steel ring rises from the overflowing Rhine, a young girl stands confidently astride its inner edge. A new beginning? We can but live in hope.

In rep to 2 November (020-7304 4000)