Garsington Opera’s compelling production of Vivaldi’s La verità in cimento (Truth put to the test) comes ‘colour coded’, possibly to help audiences unravel the intricacies of its complicated, unintentionally comic and, for most people, unfamiliar plot, this being the British premiere of an opera first given as long ago as 1720 in Venice.

Inverted commas are required because David Freeman’s production (designer Duncan Hayler) is in fact almost entirely monochrome. The setting for the action throughout is a huge white-walled conservatory dominated by a white leafless tree whose boughs span almost the width of the stage. With the exception of Sultan Mamud’s mistress Damira (Diana Montague), whose gowns and hair are red — appropriate for a scarlet woman — the costumes are black, white or shades of grey.

The story revolves around Damira’s son by Mamud, Melindo (Yaniv d’Or), and Zelim (James Laing), the legitimate heir born — crucially on the same day — to the Sultana Rustena (Jean Rigby). Both 25, they look like rock stars but (each being played by a countertenor) sing like angels.

Of the two, Zelim is much the more angelic — in voice as well, as it happens. A real Mr Nice Guy. He gets to wear white trousers. Melindo is a nasty piece of work. He struts, snake-hipped, in black leather strides. Mr Mean.

But then he has plenty to be nasty about. All his life he has been brought up as as heir to the sultanate, he and Zelim having been switched at birth, as Mamud’s sop to Damira. As the opera begins, the Sultan (tenor Paul Nilon) announces that he will reveal the true situation.

Besides the realm, Melindo stands also to lose his fiancée Rosane (Ida Falk Winland), the heiress to the neighbouring sultanate. She has previously had a fling with Zelim, too. She still has divided loyalties, which are reflected in her dress — one black boot, one white; ditto, her gloves. She is quite prepared to adjust her wedding plans to take account of the new situation.

“I shall not let fidelity to you come in the way of my happiness,” this fickle young lady sings with thrilling directness to Melindo — in Italian, of course, and most beautifully.

In fact, a compromise is achieved, allowing this richly musical production to end on a happy note, the stage bathed in bright light emanating — a lovely surprise! — from behind that great tree.

Never recognised as a top-rank writer for the voice (unlike his contemporary Handel) Vivaldi compensates here with superb orchestration in a style similar at times to that of such works as The Four Seasons.

Conductor Laurence Cummings encourages precise and elegant playing from the orchestra. There are especially valuable contributions from trumpeters Tim Hawes and Simon Gabriel and, in two enchanting obbligato passages, from recorder player Ian Wilson.

There are further performances on June 29 and July 1 and 4. . For ticket availability for the festival at Wormsley go to www.garsingtonopera.org or call 01865 361636.