The English Concert/Manze, St John's, Smith Square, London

Is there no end to the dazzling achievements of Handel's three and a half years in Italy in his mid-twenties?

Is there no end to the dazzling achievements of Handel's three and a half years in Italy in his mid-twenties? One might have imagined that the so-called Serenata Aci, Galatea e Polifemo, composed for a grand Neapolitan wedding in 1708, was a preliminary version of his much-loved later English pastoral drama Acis and Galatea, of 1718. But although the story, out of Ovid, is broadly the same, the music is entirely different - and even more remarkable.

Or so it seemed in this rare performance, launching the 21st Lufthansa Festival of Baroque Music in St John's, Smith Square. The introductory music, contrasting pastoral sonorities with dashing solo string passage work, already amounts to a concerto grosso in itself - with the strings of The English Concert directed from the first violin with characteristic fire by Andrew Manze.

Yet scarcely have we been introduced to the lovers than Galatea plunges into an anguished aria of apprehension, with keening oboe and bassoon obligati, sounding like a number out of a Bach passion, especially as delivered here by the contralto Hilary Summers.

The cyclops Polifemo is a far more menacing character than in Acis and Galatea. Indeed, his darkly scored aria after Galatea has escaped his clutches and thrown herself into the sea evokes his despair in a series of colossal leaps over a range of nearly three octaves. And while the young bass Charbel Mattar lacked the truly cavernous bottom pitches, he more than made up for this with the vibrant generosity of his middle and upper range.

Meanwhile Aci, cast in true Baroque high camp fashion as a soprano ranging far above his lady love, fell to Carolyn Sampson, who made something especially radiant of her lilting aria, contrasting her own melancholy with the happiness of the birds.

Granted, the work lacks the formal and dramatic neatness of the later Acis and Galatea as it also lacks the textural variety of added choruses. But what invention, ardour, unexpectedness! Naples can have heard nothing like it before.

Festival runs to 28 May (020-7222 1061)