At its core, Poulenc’s Dialogues des Carmélites is an exploration of faith and death. In a terrifying scene at the end of Act I, the old prioress loses a lifetime’s worth of faith as she dies; at the end of the opera, the nuns ascend the French revolutionary guillotine, confirmed in their religious fervour. Whether or not you share the petrifying fear of death or the consolation of religious faith, it’s a potent duality.

Robert Carsen’s production, created in 1997 for Dutch National Opera and premièring at the Royal Opera last night, is an exercise in extreme minimalism. There are no sets – the stage is a simple oblong. In all but one scene, there are few props  – an armchair for the elderly Marquis de la Force, a nun’s habit lying on the floor ready for the novice Blanche, flowers, a statue of baby Jesus. The effects are achieved by lighting and by a crowd: the Royal Opera chorus augmented by a a 67-strong “community ensemble”. The movement of the crowd is an extraordinary thing to behold: as it shifts and swirls, people and objects are revealed or taken away, or an atmosphere of wordless threat is created.

This won’t be a production for everyone, but if you grew up with the Bertolt Brecht school of drama where you’re expected not to watch a realistic representation but to draw your own insight from theatrical device, it’s fascinating.

In some moments, theatre and music came together to exceptional effect, none more so than the death of Madame de Croissy. As the novice Blanche watches in terror, the old prioress succumbs utterly to the agonies of her terminal illness. The shock of the scene is that forty years of religious conviction are utterly lost as she feels that God has abandoned her to her pain. Deborah Polaski was simply riveting. In the course of a distinguished career, Polaski has undoubtedly died many times on an opera stage, but I venture to suggest that this will have matched any of them as a visceral and intense experience for the audience. If you think that an opera singer dying slowly and musically is a cliché, think again.

Overall, however, the evening was a frustratingly inconsistent one, not helped by the misfortune of throat infections for the two main tenors. Yann Beuron, as Blanche’s brother, strove manfully and largely successfully to overcome his problems in an excellent opening scene with Thomas Allen as the Marquis, but was unable to return for Act II, and Alan Oke was also off colour. Generally, singing was good from the large ensemble cast, amongst whom two opposite characters stood out: Anna Prohaska as Sister Constance, the flibbertigibbet with a heart of gold, and Sophie Koch as the brave and terribly proper Mother Marie.

But there were other problems. Sally Matthews acted Blanche with excellence, hyperactive nervous energy streaming out from every pore. But her voice was heavily laden with vibrato and her diction often indecipherable, which mattered more than it might have done because surtitles were sparse and sometimes misleading. In some points, only one sentence in three was being translated, with inexplicable shifts in meaning (I wrote down two of several: the French word for “despise” translated to “hate” and “illusion” translated to “dream”). This is a wordy opera and subtle changes in meaning do have an effect.

I had been eagerly anticipating hearing Simon Rattle conduct the Royal Opera for the first time since 2007, and my expectations were only partly fulfilled. Poulenc’s score is a marvellous one, full of colour, occasionally quirky and always packed with vocal line and instrumental phrasing that falls deliciously on the ear. In the slower, sparsely orchestrated more rhapsodic passages, the orchestral performance was everything I might have wished for, with clarity of timbre and beauty of ebb and flow. But several of the more intense tutti passages didn’t quite make the impact they should have done, not least at the very opening of the opera. And I felt that proceedings lost their way somewhat in Act III: we should be experiencing a steady ratcheting up in tension as the revolutionary mob closes in. 

Salve Regina, the closing hymn sung as the nuns approach the guillotine, is justly famous: it’s music and theatre of great power, with a unique blend of soaring choral lines, insistent musical underpinning from the string section and the repeated metallic thud of the guillotine. It was nearly done to perfection last night – but marred by the guillotine sound effect being overpoweringly loud, swamping everything else.

Dialogues des Carmélites is a great opera, and this production touches greatness without quite grasping it in both hands. There’s a good chance, it seems to me, that it will make the most of those opportunities later in the run.