Waiting for Figaro: St John's, Smith Square, London

Would we care about Mozart if we had only the fragments? To judge from Waiting for Figaro, Bampton Classical Opera's latest foray into rare repertoire, the answer is a resounding "Yes". Der Schauspieldirektor (The Impresario/The Rivals), part of a Mozart-Salieri twin divertissement mounted in Joseph II's Schonbrunn orangery in 1786, actually postdates Figaro. But to create an inspired evening's worth, latter-day impresario-translators Jeremy Gray and Gilly French, the brains behind Bampton's zany revels in the obscure, have wrapped The Impresario around two sets of 1783 fragments: an overture and four stunning buffo movements from Lo Sposo Deluso (The Deluded Bridegroom); and half a dozen arias/ensembles, if anything even more dazzling – and including a remarkable Septet finale – from the surviving first Act of L'Oca del Cairo (The Cairo Goose).

Peter Schreier has recorded the extracts; but encountering them live at St John's, Smith Square, archly semi-staged by Gray and Thomas Guthrie, was a fresh revelation of genius. Gray, like Mozart, has a nose for fun; as the light drew in, the evening's sheer joky enjoyment waxed mightily. Gray is the sharper director. In L'Oca del Cairo, a zany story about two girls pent up in a tower by a grizzly old rotter and pursued by two tenor lovers who rescue them, he uses Guthrie's notable onstage comic and vocal gifts to classic effect. Watching him, Mark Saberton (as the misery guts) and soprano Amanda Pitt is a bit like seeing The Beano recycled as opera. On form, it's a hoot.

Bampton, making its first metropolitan sortie, now has a new, and deserved, London following. But it wasn't just the funnies. The orchestra, conducted by Edward Gardner, was even more remarkable. Gardner marshals his period players with the assurance of his near namesake, John Eliot Gardiner, and distils more affection. The string tone was superb; everyone excelled. Horn glitches in L'Oca's overture were eclipsed by horn brilliance in Eugenia's aria from Sposo; Pitt, who mastered the role at Bampton's outdoor premiere, just lacked sufficient weight and tone (though not range).

Saberton capitalised on the St John's aircraft-hangar echo in Don Pippo's "Siano pronte alle gran nozze", whose number patter ("32...33") prefigures both Figaro and Don Giovanni. Betsabee Haas comfortably won the Impresario soprano contest over Ilona Domnich, despite the latter's lovely top notes. But the abiding memories are tenor Mark Wilde's "She's as pretty as a picture", slightly overweighted by orchestra; Gardner's glorious string accenting for the Sposo trio; and Gray's deftly staged finale, with chorus and trumpeting brass consigning the dastardly whole lot to the clink.