When you see the All's Well that Trevor Nunn has provided at Stratford, you wonder why it should have been considered for so long as a problem play, not funny enough for a comedy, not sentimental enough for a romance, not bitter enough for a moral satire. Nunn's production, so beautiful to watch, so clear in its intentions, floats many of the difficulties away, so that we can feel the underlying tug of ironic realism. This process of clarification has been helped, believe it or not, by placing the play within a very recognisable context, a kind of fin-de-siècle mishmash, a glossy Edwardiana, more hindsight than Forsyte.

The past trouble with All's Well was that we had the wrong expectations. The story looks so much like a fairy-tale. Helena, the daughter of a poor physician and a mere dependant, marries the man she loves, Bertram, who just happens to be the heir of the Rousillon estates. And, of course, she has to go through hell for him, like Richardson's Pamela, but she triumphs in the end. She is a nice, as well as determined, girl, and we cannot understand why Bertram should not recognise her qualities immediately, despite her lowly station. In the end, however, he comes to his senses and all's well.

What goes wrong with this plot, from a romantic point of view, is that Helena's methods are unscrupulous and that Bertram's response is unchivalrous. When Bertram finally swears to 'love her dearly, ever, ever dearly', it is about as convincing as a deathbed repentance, and Edwardian critics, who for the most part considered the play in bad taste, were not slow to point out that such changes of heart are not to be trusted. What else could Bertram say? The King, whom Helena cured, had ordered him to marry her and when, as a gesture of defiance, he refused to consummate the marriage, Helena had substituted herself for one of his amours and accordingly become pregnant. The man was clobbered.

Nunn spotted the connection between this unelevating theme and the preoccupations of Edwardian theatre, notably in Shaw's Man and Superman, where the device of the anti-sentimentalists was to have the woman chasing the man. Having thus settled upon the context, Nunn explores the other parallels between the periods—such as the public-school brotherhood among the men for whom wars were a natural extension of Eton's playing fields, the roaming around Europe in search of sex without too much trouble, the humiliation of Parolles as the Billy Bunter within the ranks—and to set the seal on this conjunction, he persuaded John Napier to provide a superb conservatory set, where the slender arches and filtered light evoke both the splendour of Victorian iron-and-glass architecture and the glories of the Renaissance palaces which the Ruskinites so loved.

It is marvellously effective, but bright ideas (and, yes, it has been tried before) do not necessarily lead to good productions. This Edwardian All's Well, however, brings out those nagging questions which, although embarrassing, are the strength of the play. In a society where so much has been given to men like Bertram, isn't Helena entitled to use her wits to redress the balance? All's Well harps on matters of class and sexual antagonisms in a manner which, through our ignorance, we are inclined to think modern. The two moral laws, for there are at least two, which pervade our sexual behaviour still, only seem to be reconciled at the end of All's Well; and the title is as wry a joke as can be found in the annals of courtship.

The acting needs a column to itself. There are two performances which pull the production into perspective—Peggy Ashcroft's Countess who represents a mature gentility, prepared to moderate life's inequalities in the interests of a natural order, and Stephen Moore's Parolles, the self-indulgent exploiter of an unmerited privilege. Mike Gwilym's Bertram is a tough and attractive male rebel, while Harriet Walter's Helena is not too sweetly submissive to belie the resolve in her character. I do not wish to overpraise, but this production seems strong enough even to draw the public to the new Barbican theatre, where it must eventually arrive.