Complete performances of Semiramide are as rare as hen's teeth. Even at La Fenice – where the opera was given 28 times following its 1823 première, sometimes four nights in a row – cuts were inflicted, depending on the vocal state of the singers. This caused such public unrest that police intervened, compelling the cast to sing! For London, Rossini insisted that Semiramide “should be performed in its entirety, just as I wrote it for Venice.” Due to the vagaries of Proms scheduling, Opera Rara wasn't quite permitted enough time to manage the whole thing, but came damn close.

Under the watchful eye of Sir Mark Elder at the Hanging Gardens of Kensington, the Orchestra of the Age of Enlightenment launched into the pot-pourri overture, crisply played, its long crescendo skilfully teased out. The overture may be a fun toe-tapper, with plenty of action for the triangle, but the opera itself is a serious business, based on a tragedy by Voltaire. Fifteen years before the start, Semiramide, Queen of the Babylonians, conspired with Prince Assur to poison her husband, King Nino. Plagued by guilt and pestered to name an heir, she is drawn to the youthful officer Arsace, unaware that not only is he her long-lost son, but that he has sworn vengeance for Nino's murder. Things take a tricky turn when Semiramide proclaims Arsace as both her heir and her new consort, with Assur and Arsace bent on destroying each other. Mother and son are reconciled, and Assur suffers a protracted mad scene. Arsace plans to kill Assur, but instead strikes his mother dead – it's dark and dingy in the mausoleum's vault! – and is proclaimed king.

Italian critic Rodolfo Celletti declared that Semiramide was “was the last opera of the great Baroque tradition: the most beautiful, the most imaginative, possibly the most complete; but also, irremediably, the last.” It is packed with showpiece arias and duets for the central trio. Russian coloratura soprano Albina Shagimuratova was as lustrous as her dazzling gown in the demanding role of Semiramide, composed for Rossini's wife, Isabella Colbran. It's an ample, bright, aristocratic voice, filling the Albert Hall with ease. Bravura top notes were executed with fearless laser-like accuracy in a ravishing “Bel raggio lusinghier”, her showpiece Act I aria. Daniela Barcellona's dusky mezzo-soprano offered neat ornamentation and agility aplenty as Arsace, swelling her tone as she hit the throttle impressively in a terrific Act II cabaletta “Sì, vendicato il genitore”. Shagimuratova and Barcellona shone in their duets, the “Alle più care immagini” section of their famous Act I duet seeing their coloratura perfectly matched.

Bass Mirco Palazzi, a late replacement for Ildebrando d'Arcangelo, was a light-voiced Assur, fumbling for the low notes, but negotiated ornamentation nimbly, even if Rossini gives him little opportunity to draw breath. He didn't quite wrench the pathos from his mad scene but it was creditably sung. Gianluca Buratto's sepulchral bass made much of the high priest Oroe. As Idreno, Barry Banks (an even later replacement for not one, but two tenors) scaled the wilder Rossinian peaks as if out for an afternoon stroll. He displayed lovely soft tone in his Act 2 aria “La speranza più soave”, even if coloratura threatened to veer off-course. His Act I aria was a casualty of performance cuts, but was hopefully reinstated in the studio recording made earlier in the week.

Captain of the guard Mitrane (David Butt Philip) and Princess Azema (Susana Gaspar) are given short shrift by Rossini – and even shorter shrift here, with some of their recitatives chopped. James Platt made the most of his ghostly appearance as old king Nino, his bass thundering louder than usual via a microphone echo-effect as he appeared among the Prommers in the Arena to haunt Semiramide.

A few wobbly horn moments apart, the OAE played tirelessly throughout the near four-hour performance, holding out longer than many of the audience, who crept away early to catch Sunday night transport home. Elder found silky lightness in Rossini's score, with colourful woodwind roulades dispatched with character, exciting martial brass, and thrilling timpani playing from Adrian Bending. A feast of Rossini, greedily consumed in a single sitting.