When Emperor Überall decrees an all-pervasive war that will result in the death of his whole population, Death takes umbrage at the fact that his job is being usurped and, in the mother of all demarcation disputes, goes on strike. Death, it turns out, is something of a stickler for procedure, refusing to take away his friend the Harlequin because his name isn’t on the list yet; he and Harlequin coolly observe proceedings as soldiers are unable to kill each other, eventually forcing the Emperor to confront the nature of his regime and of war itself.

Viktor Ullmann’s The Emperor of Atlantis veers between surrealism and satire, straying too close to the latter for the liking of the Nazi authorities in Terezin, the concentration camp in which it was composed. Eventually, Ullmann and his librettist Peter Kien were transferred to Auschwitz, which they did not survive; it’s something of a miracle that rehearsals of The Emperor of Atlantis got as far as they did and that enough of the score survived, somehow smuggled out of Terezin, for the work to be reconstructed - although it was not until 1975 that it received its première in Amsterdam.

English Touring Opera’s production, directed by James Conway and opening at the Royal Opera House’s Linbury Studio Theatre, gets nearly everything right, and were it not for one major flaw, would have made for an absolutely must-see evening of opera. The music, conducted by Peter Selwyn, is a mercurial mix which, in the best traditions of early 20th century, obeys no barriers. Melodies are strong, the timbre and phrasing shifts to disturb you, elate you, amuse you or make you feel nostalgic, all done on an eclectic selection of instruments which matches the selection of what would have been available in Terezin - violins, clarinets, banjo and guitar. There are hints in the music of Martinů and Kurt Weill, snatches of popular style, a Bach-like chorale at the end.

Sets and costumes are simple and extremely effective - Death in the guise of an old soldier, in whiteface and grey hair, carrying a rifle with a long bayonet curved into what might be a scythe, the Emperor in full dress uniform seated in front of a giant military map, Harlequin in traditional clown costume, rather too padded and rather too grubby.

The Emperor of Atlantis is a short work, but one of great intensity both intrinsically and because we know the history of its composition. Rather than distract us by juxtaposing it with another one act opera, ETO chose to preface it with a Bach cantata Christ lag in Todesbanden, giving us a work of similar intensity (and providing a neat counterfoil to the opera's closing chorale). The cantata was performed in a particularly edgy style, using four of the cast of the opera and watched over by the Emperor, Death and Harlequin with a choreography designed to disturb us even as Bach’s marvellous music elated us. It had precisely the desired impact.

The performance of the music, by the Aurora Orchestra, was top class, vibrant and punchy, and the seven singers were all superb, with strong, lyrical voices that delivered their lines with passion. Acting and movement were also excellent. It’s hard to pick out individuals, but from a purely vocal point of view, I was impressed by Katie Bray as “the Drummer” (the voice of military madness). Robert Winslade Anderson had huge stage presence as Death, as did Richard Mosley-Evans as the Emperor. He didn’t much to do at the beginning of the opera other than to sit behind his desk giving instructions, but when he emerged from behind desk, Mosley-Evans took over proceedings with a splendidly powerful baritone sound.

But this production has an Achilles heel: poor diction. A conceptual, wordy narrative like The Emperor of Atlantis is absolutely reliant on the audience being able to understand what the characters are saying, and although this was being sung in English, I spent far too much of the evening straining desperately to make out the words. The spoken dialogue was fine, of course, but there was a great deal of the singing where, try as I might, I simply couldn’t catch the meaning. It may be possible for singers to get away with this level of diction when performing standard operatic repertoire where they might expect the audience to know libretto (although even that raises questions of how you attract new audiences), but anything other than crystal clear diction makes it very difficult to fully appreciate a dramatic opera being seen for the first time without the benefit of lengthy advance study.

As The Emperor of Atlantis goes out on tour, I hope that this is something that its cast can improve, and maybe it will be better in other venues or to younger ears than mine. This is a high quality production of an opera that is powerful and fascinating, with excellently performed music that excites. Without the constant struggle to make out the text, it may well have been one of the best things I’ll see all year; as it was, I left disappointed.