Pia de' Tolomei premiered in Venice in February 1837 and, unbelievably, reached London in March 2016 – last week – a mere 179 years later. With laudable courage, English Touring Opera has once again dived deep into the Donizetti back catalogue and come up with a pearl of luscious beauty. While Donizetti's work is rightly prized in the operatic canon, occasional pieces have slipped through the net, partly because he was simply so prolific; but how this ferociously dramatic, exquisitely beautiful work was ever overlooked is a mystery once you've seen it. ETO's production gives us that rarest of opportunities: a superb evening of opera at once recognisably gorgeous, in the highest traditions of bel canto, but also entirely, refreshingly new.

Director James Conway's characteristically clear-sighted approach makes the most of the human drama at the heart of this opera: a husband and wife still passionately in love with each other, but separated by a fundamental misunderstanding and then kept apart by their own pride. Pia, a daughter of the Pope-supporting Guelph family, the aristocratic Tolomei, has been married to Nello della Pietra, a Ghibelline (a supporter of the Emperor) and her dynastic enemy, in an attempt to broker peace between the warring factions; while that intention doesn't work out, the marriage certainly does, until Nello is led to suspect Pia of infidelity when a letter reveals she is meeting another man in secret. That man is, in fact, no lover, but Pia's brother Rodrigo, on the run from a Ghibelline death sentence: Pia's chastity is meanwhile under constant assault from Nello's kinsman Ghino, who desires her obsessively, to her horror. Ghino decides to destroy Pia after her repeated rejections, showing Nello the fateful letter and ultimately provoking her death on Nello's orders, but not before she has managed to join her husband's and brother's hands together in an oath of peace, ensuring the end of the Guelph-Ghibelline war with her dying breath, finally exonerated from all blame by a shattered, repentant Nello. Donizetti screws the tension higher and higher all night, using brazen martial marches and occasional sour harmonies to contrast with soaring ideas of love and duty, which are picked out beautifully by the orchestra, conducted with energy and care by John Andrews.

Loren Elstein's design uses tall scaffolding-like structures, some straight and some leaning at threatening angles, to infuse all scenes with a sense of precariousness and industrial brutality. While the set never actually shifts, Guy Hoare's lighting cleverly changes its emphasis from scene to scene, using a column of light for Rodrigo's prison cell, or highlighting certain angles to indicate the warren-like caves of the hermits who plead for God's mercy on Nello (and Nello's mercy on Pia). Costumes vary from a deconstructed Medieval silhouette for warriors and servants, to Napoleonic frogging for Ghino: this evokes various conflicts across time without being specific, though we do get a very Medieval shimmering silk banner for the wretched Guelphs to rally around.

This is definitely an opera which rises and falls with its star, and Elena Xanthoudakis is truly fabulous as Pia, doing the role glorious justice with her stellar projection, wonderful softness of tone and huge soprano range. Her dramatic instincts are keen, delivering a performance as heartbreaking as it is stunning. Grant Doyle is in magnificent voice as Nello, his burnished baritone sounding ever richer and his Italian beautifully clear. Catherine Carby is truly affecting in the trouser role of Rodrigo, her honeyed mezzo an absolute luxury in Rodrigo's tragic imprisonment aria. Luciano Botelho is engagingly clear and focused, but just a little underpowered in comparison to his companions as Ghino, not always making it over the orchestra but still giving a good idea of a man consumed by erotic obsession which turns to hatred, and finally, to near-suicidal remorse.

Smaller roles are less consistently strong (Ubaldo lacks power, Lamberto could do with more colour), but the magnificent performances of Xanthoudakis, Doyle and Carby keep this opera firing on all cylinders until the very end. The Chorus has wonderful tone and punch as warriors and servants; some slightly lacklustre flagellating strikes an odd note in the hermit scene, but is soon saved by Piotr Lempa as a striking chief hermit. With nothing otiose in its dazzling bel canto beauty, this opera is dramatically compelling, historically fascinating and profoundly moving, and above all, worth seeing for its astonishing central performances.