Cosi Fan Tutte, Coliseum, London

An opera that tells the truth about love

What do you suppose happens after the final curtain has fallen on Così fan tutte? Have our young lovers really learned to "smile at life's adversity"? Will peace and love "win the day" for them? The last thing we see in Matthew Warchus's deft and illuminating new production for English National Opera is Don Alfonso handing over money to Despina, the maid. She spits on it. After a lifetime of taking backhanders for services rendered, she, for one, has learned something at the "school for lovers". No one graduates unscathed. The sequel – had Mozart and Da Ponte written it – would have been very messy indeed.

Actually, Warchus gives us the prequel – or at least a premonition of such. While Mozart's orchestra chortles away during the prelude, we discover Don Alfonso, alone and pensive in his baronial hall, the walls parting to reveal what may or may not be our lovesick protagonists picked out in the darkness, their heads swathed in dark cloth like unfinished puppets. They are faceless, interchangeable pawns in some sort of game. And who are the two dark strangers waiting in the shadows? Patience. Don Alfonso, the puppet-master, is all set to begin his demonstration.

My first reaction to this prelusive dumb-show was twofold: distracting; too sinister, too soon. A tricksy directorial device. But then it struck me how interestingly the busy geniality of the music played off these rather creepy images. The music smiled, the images didn't. They say that opposites attract: in Così, they co-exist. Humour and heartache, pathos and bathos. So Warchus and his really top-notch cast quickly won me over. This is as good, as truthful, as amusing, as wistful, as painful a Così as we might reasonably expect in our cynical times. The key to its success is, as ever, simple truth. It isn't funny because it tries hard to be, it isn't touching because it elicits our sympathies. It's both because the people are real. They think, they feel, they hurt.

With Jeremy Sams's spanking translation blithely going to any lengths for a good rhyme – yes, the "vernacular" really is "spectacular" – Warchus and his cast make every word count. The honesty and naturalism, the deftness of the playing is picked up in Laura Hopkins' exquisite designs – all sepia shades of brown delicately fading like the first flush of romance. Clouds and porticoes dominate the skyline. The dating is the 1930s, which makes something more immediate of the boys going off to the front to fight the good fight.

But, like I say, it's the humanity that makes this such a stand-out Così. When Susan Gritton's gorgeously feisty Fiordiligi wrestles with temptation in her great second-act aria, the introspection she brings to it takes us painfully close to her torment. She doesn't really have the bottom notes for either of her show-stopping arias, it's true, but she colours very cleverly to disguise the fact and with a conductor as sensitive to his singers' needs as Mark Wigglesworth, there are considerable gains in intimacy. Mary Plazas also shines as Dorabella, whose righteous indignation crumbles beneath her susceptibility to chocolates and fox furs. As Ferrando and Guglielmo and their pastel-suited, moustached alter egos, Toby Spence and Christopher Maltman are sexy and stylish. And who but Andrew Shore (Don Alfonso) could simultaneously raise a laugh and turn your stomach with a line like: "These are your lovebirds, even if their wings are a little soiled."

Which just leaves Janis Kelly's marvellously knowing, seen-it-all Despina. When she spits on Don Alfonso's money, she does so for all female victims perceived as guilty until proven innocent. Così was premiered in 1790. What's new?

To 4 July (020-7632 8300)