When you think chic, black-tie country house opera, you probably don’t also think sixteen barefoot nuns being executed. Grange Park Opera’s fusion of these two contrasting ideas, however, has a lot going for it: their production of Francis Poulenc’s Dialogues des Carmélites combines its minimal but effective staging with some impressive singing.

This is an opera which lends itself to rather stark productions, after all – it’s set predominantly in a convent, and most of the cast are nuns. It tells the story of the sixteen Martyrs of Compiègne, Carmelite nuns who were guillotined by French revolutionaries for their lack of support. Focusing in on one particular young nun of aristocratic background, Blanche, the opera is effectively one long crescendo up to the execution scene, in which the nuns process out one by one to face their deaths, while singing the Salve Regina. There are plenty of strangely moving finales in the operatic canon, but this is one of the most searing, and Poulenc’s uncontroversial but deeply compassionate score makes the whole thing a remarkable set piece.

Director John Doyle’s interpretation of the opera takes the very Carmelite idea of simplicity, and runs with it, seldom interfering with the opera’s straightforward storytelling. Liz Ashcroft’s spare set is static for most of the opera, a couple of chairs doing a large part of the prop work, the high, pale walls intimidating in their bareness. The lighting, by Paul Keogan, is as striking as any of the other elements if not more so, deftly conjuring different worlds through shades and subtle shifts. A single, thin shaft of light cuts across the large back wall; soft, projected silhouettes of Jesus on the cross occasionally appear above.

A respectful staging, then, and it had more than respectable singing to accompany it. Leading the cast was Hye-Youn Lee as Blanche; her very strong, full soprano capturing the steadfast nature of her character. I felt a touch of vulnerability might have furthered her interpretation of this young, strangely zealous woman, but vocally this was an excellent display. Her friend Constance, another soprano, was played by a radiant Soraya Mafi – Constance was apparently Poulenc’s favourite of his nuns, and he certainly gave her the sunniest music. Mezzo-soprano Anne-Marie Owens gave a brilliant deathbed scene as the veteran Prioress, delivering this gripping speech of final doubts with terrifying intensity. But the cast was strong as a whole, with secure and impassioned singing all round – the contributions of Nicky Spence, Fiona Murphy and Sara Fulgoni also stood out. The occasional choruses, all the more powerful for their infrequency, were mesmerising.

While Stephen Barlow’s conducting appeared equally assured, the English Chamber Orchestra’s playing was this production’s weak link, with intonation and timing issues creeping in with increasing regularity throughout the evening. Poulenc’s sweet, tonal score is a deeply indulgent thing – even the programme notes point out with some bafflement that this 1957 opera is roughly contemporaneous to Boulez’s Le marteau sans maître – and it was a shame not to be able to wallow in the easy beauty of its harmonies. But that said, the vocal performances ensured a high quality of music-making overall.

Technical problems hampered this particular performance, delaying the start time by over two hours – we ate before the opera, rather than in the customary 90-minute interval, and between Acts II and III we were asked to stay put and “pee in the seats” if necessary. This might sound pretty bad, but all was dealt with in an impressive, genial way – it would all have been fine, had the delay not led to us missing the last train home. Still, at least we weren’t executed by French revolutionaries.