POPE CLEMENT VII (1523-34), whose dramatic emergence forms a central scene in Hector Berlioz's opera Benvenuto Cellini, which is being staged in a new production by English National Opera at the London Coliseum, was a pontiff who had his share of bad luck. But, being born Giuliano de' Medici, and bearing the same name as his late father - assassinated in the Duomo at Florence at the age of 25 - and nephew of the great Lorenzo, he perhaps knew a bit about art.

One of four Medici popes to hold sway in a century, Clement had been, in effect, Leo X's Rottweiler. Because he was Florentine, he accentuated the rivalry between the two artistic and commercial centres Rome and Florence that forms the heart of this powerful, hugely entertaining, but rarely seen opera, which flopped on its Paris première in 1838.

Clement's bossy appearance puts the sculptor Cellini on his mettle. Clement is sung by the baritone Willard White, in a role dangerously veering towards camp-comic in this two-act opera semiseria; and what a joy it is to hear the overture convert into a full-blown aria, richly intoned by the striking American tenor Michael Spyres - a singer shamefully unknown to me, but much admired for his appearances in New York, Dresden, Salzburg, and the Rossini festival in Pesaro.

Cellini has been commissioned to complete a bronze statue of Perseus - the famous statue still to be seen in the Piazza della Signoria in Florence - and must complete it, pronto, or face execution. A gallows even appears high above in the director-designer Terry Gilliam's very witty, funny, and astute - if sometimes cluttered - ENO staging; and ominous chaps pace up and down, preparing for the grisly moment.

But we know it will not come. First, it is hard to believe that a sumptuously arrayed Holy Father wheeled forth aboard a kind of minbar and looking like the Emperor from Turandot is going to give him the chop.

Second, because Gilliam is best-known to us as the pictorial member of the Monty Python team (those flamboyant cartoons), he treats us to a huge amount of visual tickling. If occasionally this fiesta gets addled or out of hand, what are artists' studios (probably including Gilliam's own) if not awash with bric-à-brac?

The singing is pretty fine, starting with Pavlo Hunka's elegant, severe, and commanding Papal Treasurer, Giacomo Balducci, who has plans to marry his daughter Teresa (Corinne Winters) to a rival sculptor-cum-dilettante, the ghastly Fieramosca (perhaps "pompous bluebottle"), who wants both the girl and Cellini's commission, but is gloriously inept. Hence flows comedy well worthy of Rossini.

Delightfully though Winters (also an American) sings, I fell vocally for young Irish mezzo Paula Murrihy as Cellini's patient assistant Ascanio. Trouser roles invariably have that certain buzz, but her acting, full of little touches, proved deft and charming.

The American Nicholas Pallesenas Fieramosca is another vocal treat, proffering great beauty amid the blustering: a wonderful, classic loser. There are agreeable lesser roles: scribes, chaperones, harridans -mostly in drag; and both ENO male and female chorus sections have fine individual moments, having been prepared up to the gills by the chorus master Nicholas Jenkins, who is aide to the Baroque specialist Marc Minkowski, and closely associated with both the Dutch National Opera and opera at Blackheath Concert Halls.

High praise goes to ENO's orchestra desks, ever fleet of foot and artfully driven and paced under the outgoing music director Edward Gardner. One papal passage for cellos and double basses excelled, and the subtlety of Gardner's brass felt particularly pleasing in a composer whose inflated scores tend to encourage bellowing.

But it is Gilliam who gets thingsso blissfully right, by deciding that the central character should be the statue. We see the gold head of the Greek hero, modelled enticingly closely on Cellini's somewhat Apollinian 1545 original. From the start, bits of gold keep turning up. And, as we approach the Pythonesque dénouement, the whole stage, with back-projections and astounding animations, becomes a seething smelting and casting forge that is as dramatic and fiery as Coalbrookdale by Night.

Aaron Marsden has helped Gilliam forge some stupendous sets. Katrina Lindsay's saucy costumes are both an education and a marvel. Paule Constable's lighting is, as always, spot on the mark. Leah Hausman's movement direction is endlessly shrewd and clever. I reeled out, magnificently exhausted.
 

Benvenuto Cellini is at the London Coliseum, St Martin's Lane, London WC2, until 27 June. Box Office: phone 020 7845 9300. www.eno.org