I love light opera in all its forms – buffa, operetta, opéra-bouffe – and I wish that more of it were staged. So the Royal Opera’s production of Emmanuel Chabrier’s L’Étoile seemed to have all the right ingredients: a great score, stunning visuals, a decent sprinkling of French singers in the cast and a generous dollop of silliness. Any opera with a main character named Hérisson de Porc-épic (Sir Hedgehog of Porcupine) should, in principle, get my vote. Sadly, you can’t judge a cake by its ingredients, and this particular cake failed to rise.

The biggest success of the night was Julia Hansen’s designs. Hansen happily allowed fairy-tale and real-world Belle Époque to collide on stage with abandon, with more than a passing nod to Terry Gilliam’s animations for Monty Python. De Porc-épic’s ambassadorial party, dressed à la Phileas Fogg, arrives in a cardboard cut-out balloon. The (thinly) disguised King Ouf is pointed out to the audience by a giant Pythonesque cardboard finger. Storytelling is framed by heavily gilt Persian painting straight out one’s favourite story book of The Arabian Nights. The lovers elope on a cardboard speedboat bouncing over cardboard waves. It was a good production to look at.

It was not, however, a good performance to listen to. Sir Mark Elder chose deathly leaden tempi and seemed unable to coax the ROH orchestra into achieving any kind of orchestral brilliance or attack: a score that should bubble and sparkle did nothing more than meander. But there proved to be an even more fatal flaw: intelligibility. The vast majority of the humour in L’Étoile lies in its wordplay: if we can’t hear the puns and rhythmic games being played, there isn’t a great deal left. Unfortunately, the policy on surtitles seemed to be to provide brief translations for one sentence in three. Non French-speakers would have had no chance whatsoever of getting the gags. French speakers (of whom I am one) stood a chance only if the singers had pin-sharp diction.

In this, one member of the cast stood out: Christophe Mortagne was consistently funny as King Ouf, as well as bringing to the party a pleasant, bright tenor. François Piolino’s Porc-épic was adequately audible, as was Simon Bailey as Siroco the astrologer (impressively, as the only non-French member of the cast to do so), and Bailey also gave us some entertaining gravelly low notes. But it was impossible to understand more than the odd word that the chorus was singing, and in the two key roles of Princess Laoula and Lazuli, the humble pedlar who wins her love, things weren’t much better. Hélène Guilmette has an attractive voice, but consonants were slurred. Kate Lindsey’s voice is lovelier still, but lack of consonants added to indifferent French pronunciation to remove any possibility of understanding the humour in Lazuli's lines.

While Elder dragged proceedings from the musical side, Mariame Clément did nothing to inject pace in her direction of the acting. Stage movement was less than crisp, choreography of the can-can pastiche was sloppy. The intervention of a pair of comedians to explain what was happening to the audience served only to slow down the action further. The supposed gag was that the audience couldn’t possibly understand all this French farcical nonsense, but I couldn’t suppress the thought that this was all too accurate, and that if a director needs to freeze-frame the action in a farce in order to explain to the audience why they should be finding this funny, something is seriously awry.

Staging L’Étoile at Covent Garden was a brave decision – “brave”, that is, as used by Sir Humphrey from Yes, Minister. It could have worked out just fine, but that would have needed fanatical attention to keeping things pacy and upbeat. It also would have either needed singers – including the chorus – committed to making every word understandable, or far more creative use of surtitles to bring out the wordplay. Those things just didn’t happen, making for a disappointingly flat evening.