After the sexual and power politics of the Roman Imperial family, it is quite a relief to observe the eternal love quadrilateral, albeit á la Grecque with magic and gods. The third of English Touring Opera's season of Venetian operas is Jason, by Cavalli and, on the evidence of this production, the most fun.

Some of that fun is provided by a stammering hunchback, which makes a virtue of the baroque repetitions, and adds a touch of realism to some of the information-imparting conversations between Demus (the stammerer) and Orestes, who tries to finish Demus's words. Piotr Lempa, who has some lovely deep notes as Orestes, and Stuart Haycock, as the stuttering Demus, let the words - in Ronald Eyre's witty translation - and music make the joke.

The information concerned relates to Jason, who has left his wife Isiphile and children on Lemnos in search of the Golden Fleece. On the way he has met Medea, in Colchis and the opera opens on the wedding night. King Egeus, Medea's husband, had despatched Demus to see if Jason were there. Orestes had been sent by Isiphile, also to find out what Jason is doing.

Samal Blak's set shows the entrance hall, staircase and landing of a grand-ish house, all done in a creamy white. In Colchis, it is bedecked with garlands and a wedding cake on a table; in Lemnos, trees grow through the windows, leaves gather in corners and the bannister rails are broken and missing.

Catrine Kirkman plays Isiphile as a bit drippy; one can understand Jason's preference for the more assertive Medea - Hannah Pedley in white reminiscent of Pippa Middleton's bridesmaid dress. Jason's bovver boots, however, are an irritation and do not go with his suit or sword.

Despite Kirkman's tendency to be slightly shrill on her top notes, her poignant farewell to her children is deliciously sung and the duet with Medea, where they sink their differences, is warm and generous. Clint van der Linde produces a tough edge to his voice - particularly in dealings with Hercules - emphasising macho Jason the action hero.

As Hercules, Andrew Slater is maybe not intellectually challenged enough to merit Jason's tellings-off, but wins our sympathy with his dawning realisation that (a) he has thrown the wrong woman into the ocean (Medea bundled unceremoniously out a window) and (b) he is not about to compound his fault by killing another woman.

Like the abandoned Isiphile, King Egeus is a bit pathetic, pleading with Medea to return, but John-Colyn Gyeantey's nice guy deserves to get her back in the end, as he does. Michal Czerniawski's servant Delfa has a resemblance to Professor Brian Cox the astronomer, particularly in gesture. The occasional off-stage ensembles sound gorgeous.

Director Ted Huffman uses a nice illusion to indicate the storm which precedes Act 2, together with some clever lighting from Ace McCarron and prologues from Apollo (Haycock) and Cupid (Czerniawski), to remind us of the magic. And there is more magic from the Old Street Band, conducted by Joseph McHardy.