Das Rheingold, Royal Opera House, London

A starter that leaves you hungry for more

Conducted by Antonio Pappano, designed by Stefanos Lazaridis, lit by Wolfgang Göbbel, and featuring Bryn Terfel's debut as Wotan, Keith Warner's Royal Opera House Ring cycle is the most eagerly anticipated operatic event of the decade. But Das Rheingold is merely the amuse-gueule. It may seem strange to refer to two and half hours of music like this but it is worth remembering that this opera was conceived as a "preliminary evening". Here we have a composer sketching the backstory to an epic to be performed over four consecutive nights to an audience ignorant of cinema; raising many questions and resolving none of them. Which is not much help to a production team who are expected to deliver something that can satisfy a cinema-literate audience and stand alone as an entertainment until 2007 when the Covent Garden Ring is performed in its entirety.

Warner and Lazaridis's source-book is eclectic; with images recalling the films of Fritz Lang, Orson Welles (Terfel's harried, handsome Wotan is strongly reminiscent of the young Kane in Citizen Kane) and Ingmar Bergman, starscapes extrapolated from NASA space probes, an enigmatic spiral of DNA (down which Günter von Kannen's Alberich paddles his dinghy), and the self-flagellating performance art of Günter Brus. Marie-Jeanne Lecca's costumes are similarly diverse; ranging from the shimmering prelapsarian nudity of the Rhinedaughters, to the bel epoque evening wear of the gods, and on through 40 or more years to the lab-coats and cardigans of the dwarves. It is a rich and conspicuously expensive palette, and there are moments of theatrical magic in Das Rheingold: the faint light of the gold in the first few bars of the prelude, its bursting brilliance, and the flexible net of blue light that suggests the waters of the Rhine; the toiling Expressionist shadows of Alberich's still invisible work-force; the solarized cloudscape beyond the windows of Wotan's black marble palace. But there is a chasm between these assured design effects and the near-burlesque execution of some of Warner's other ideas.

The giants' entrance is cleverly set up with silhouettes but Fasolt (Franz-Josef Selig) sports earthy, extended fingers and clownishly elongated, dirty feet, while Fafner (Phillip Ens) reveals a hideously distorted conical pate when he removes his stove-pipe hat. In a movie, you could imagine swallowing this blunt grotesquerie. But in a movie a director could control his audience's viewpoint through careful editing. On stage, there is no such control.

In the third scene's audacious coup de théâtre - in which the entire stage is lifted to reveal the laboratory where Alberich and Mime (Gerhard Siegel) perform their pseudo-scientific medical experiments - Warner flirts still further with carnival excess. Latex body parts litter Nibelheim, along with lobotomised zombies whose acting is a little too effortful for my taste. Alberich's transformation into a dragon (achieved laboriously with three actors in progressively larger prosthetics) and an animatronic toad brings to mind the Victorian freak show: clumsy, corrupting, vulgar, voyeuristic. Doubtless this is intentional. We should feel disgusted and repelled by Nibelheim. But the theatrical business is less suggestive than that first brief glimpse of the hammering shadows, and is strangely at odds with Warner's calm unfurling of the individual characters.

Excepting the moment where the gods gather for a slide-show of Loge's travels, Warner's most successful scenes are one-on-one dialogues (which bodes well for Die Walküre). The exchanges between Wotan and Fricka (Rosalind Plowright) are surprisingly tender. Theirs is an old marriage but one that has yet to dissolve. Plowright's acting is magnificent: her expression beautifully judged as she leaves for Valhalla and Wotan remains for a highly unlikely coupling with Jane Henschel's dowager-like Erda. Fricka's old money poise contrasts with the dissipation of Froh (Will Hartmann), Donner (James Rutherford), and their fluttering sister Freia (Emily Magee), and small touches such as her barely-concealed distaste for the muddy boots of the giants give nuance to a role that is all too often frigid and flat. Terfel and von Kannen are afforded the same treatment. Certainly, this is the most sympathetic Wotan I've seen, and Alberich's self-mutilation as he curses the ring is a stroke of genius. Siegel's crazed Mime promises much fun in Siegfried, and from the girlish Rhinemaidens (Sarah Fox, Heather Shipp, Liora Grodnikaite) to Terfel's authoritative, troubled Wotan and Philip Langridge's squirrely Loge, this is a superlative and cohesive cast.

Which brings me, finally, to the conducting. Antonio Pappano's Das Rheingold is not lush, luminescent, architectural or reverential. It is instead transparent, organic, almost rhapsodic, and strikingly intimate. In the very best way, his prelude sounds sight-read. From the front of the stalls, its newness was intoxicating; the sensation one of floating in harmonic amniotic fluid. The playing of the horns was beyond compare, the ascent up through the different instruments giddying. With a relatively light-voiced cast and singing of lieder-like clarity and subtlety, Pappano's Das Rheingold is most notable for its delicacy. No, I didn't feel overwhelmed in the way I might expect to feel after Die Walküre, Siegfried, or Götterdämmerung. I did however feel seduced, surprised, provoked, and very curious to see and hear the rest of this Ring. As a preliminary evening, Das Rheingold is a striking success.

'Das Rheingold': Royal Opera House, London WC2 (020 7304 4000) to 10 Jan

a.picard@independent.co.uk