There is a fascinating moment in Francesco Cavalli’s opera about Jason and the Argonauts when one of the increasingly desperate bit-players pauses to bemoan our hero’s endless dallying with the sultry Medea and the general, hopeless inability of love to stay the course. “What older story can there be?” he sighs, never minding that in 1649 the very expression of such sentiment – in a newfangled stage concept called an “opera” – would have seemed startlingly and daringly modern.

That tells you something about the breezy confidence with which Cavalli (and his librettist, Giacinto Cicognini) set their delicious tragicomedy, which has come up a treat in Iford Manor’s beautiful mock-Renaissance cloisters. With a maximum of a ninety in the audience at this most intimate of the country-house opera festivals, the Early Opera Company’s production might not have to strive for spectacle, but it does have to draw us into a convincing world of its own – and, by and large, it succeeds handsomely.

Maybe, at first, Martin Constantine’s quickfire production heads too blindly for pure Jilly Cooper territory. As we enter, members of the audience are given cheerful stickers advertising the “sex resort” of Colchis; within minutes of curtain up Stephen Wallace’s Jason and Madeleine Shaw’s Medea are giggling under the sheets – the feckless squaddie has moved on to the next port and the next floozy, abandoning wife number one, Sinead Campbell’s desperate Hypsipile, in the process.

What happens next isn’t the story you might know from either Euripides’s bloody psychodrama or Ray Harryhausen’s claymation skeletons.

“War was my mistress, now love is my master,” laments Jason in Ronald Eyre’s adroit translation. It follows that in Cavalli’s version the quest for the Golden Fleece is banished to the interval; all heroics take second place to the characters’ emotional addictions. And, although the modern-dress setting ramps up the naughtiness, Constantine never resorts to caricature: these are very real people in a very real pickle.

It is Cavalli’s sighing, suffering music that tells us that most strongly, and Christian Curnyn’s excellent band of players do it complete justice. Winsome, plangent arias are teased out with great sensitivity; the snappier, sassier episodes pass by with a cheeky flourish. There’s no weak link in the cast, either: Wallace’s sensuous, smoky countertenor fits the dreamy Jason to a tee, while Campbell’s Hypsipile carries the torch for constancy with classy intensity.

Shaw’s powerfully voiced Medea makes a more than credible rival and the supporting cast, among them an engaging drag act (Robert Burt’s majestic Delfa, a lusty maidservant oblivious to her own grossness), are uniformly excellent. It may be more than 350 years old, but Giasone still feels terrifically alive.

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