THEATRE / Three's company, two's a crowd: The menage a trois is full of theatrical promise, and nobody has better exploited it than Noel Coward in Design for Living. By Paul Taylor

The snappiest gag about menages a trois was delivered by Groucho Marx. In Animal Crackers, he ogles a couple of starlets and quips, 'We three would make an ideal couple. Pardon me while I have a strange interlude.' He's referring, of course, to Eugene O'Neill's nine-act drama Strange Interlude (1928) and to its heroine who is torn, protractedly, between two men. Groucho's joke would work even better, though, as a gloss on Noel Coward's Design for Living, which was premiered in New York five years later with the same actress, Lynne Fontanne, in the leading role.

This comedy has a central arty threesome (Otto, Leo and Gilda) who are all equally in love with one another, who try out various permutations a deux, and eventually wind up in what Gilda's marginalised husband denounces as a 'disgusting three-sided erotic hotch-potch'. Coward's glamorous twist to what you might call the three-point turn is revived this week in a new production by Sean Mathias at the Donmar Warehouse.

The more you ponder the play, the weirder a phenomenon it looks. There has been no subsequent drama that affords a solution of such extreme artifice to those who believe that 'in love, the couple is not ideal' (as Jim puts it to Catherine in Jules et Jim, Truffaut's cinematic study of a rather less successful three-cornered alliance). The bizarre uniqueness of Design for Living is best approached by considering first how other plays have dealt with relationships that are, by accident or design, triangular.

Three's company, two's a crowd: menages a trois refuse to square with the vulnerable pairings of conventional comic form, and to that extent they are pre-emptively anti-dramatic as well as anti-social. They stand as a symbol of self-sufficent abundance, of a relationship that has already neutralised external threat by, as it were, bisexually incorporating it. The rules of romantic comedy forbid such a process. It's rather as though, at the end of The Merchant of Venice, Antonio, the older man whose offer to give up a pound of his flesh and perish for love of Bassanio represents a stiff homosexual challenge to the love Portia can offer, were to be invited into the marriage bed at Belmont.

But it's precisely because a successful threesome is so doubly including (and hence so lacking in the standard dramatic opportunities) that it can offer, when incomplete or defective, an intensely stageable image of stereoscopic exclusion. Harold Pinter is the poet of this predicament. The haunting picture at the start of Old Times (1971) is of a semi-spectral triangle. A middle-aged married couple are sitting waiting for the arrival of their guest, a room-mate of the wife from 20 years ago. In their thoughts, though, she is already heavily present, as is underlined by the fact that, to the audience, she is physically present, staring out of the window in the background. What follows is a verbal duel in which the husband and friend use real and invented memories as weapons in order to compete over the degree of intimacy each has had with the wife. It's an electric study in a husband's retrospective jealousy, his need to insinuate himself as a third party into a past where he may have been, like the title of the film there's a pointed dispute about, the Odd Man Out.

Pinter revisits the theme in Moonlight, though in a more glancing, bluffly comic vein. His protagonists, a foul-mouthed civil servant, lies on his death-bed and considers, among other things, the rum circumstance that his mistress became his wife's lover. 'Think of the wonder of it,' he tells his spouse, 'I betrayed you with your own girlfriend, she betrayed you with your husband and she betrayed her own husband - and me - with you] She broke every record in sight] She was a genius and a great fuck.'

That speech, though not without a satiric edge, is unusual in that it makes bisexuality - the pre-requisite, after all, for menages a trois - sound a robust, positive thing (like being nimbly ambidextrous) rather than a slithery, suspect business of having no special preferences either way, such as is the case with a lot of the AC-DC types in triangular drama, whether it be the young kinetic sculptor who gives Glenda Jackson and Peter Finch such heartache in the film Sunday, Bloody Sunday or the sexy amoral young thug in Entertaining Mr Sloane. Indeed, bisexuality gets a brilliantly contrived come-uppance in Orton's comedy when the brother and sister, whose father he has kicked to death, blackmail Sloane into becoming their sex slave for six months of the year each. 'Your youth pleads for leniency and by God, I'm going to give it you,' says the brother, making 'leniency' sound like 'a good seeing-to' which in this case it will be. Sloane's ambiguous appeal, hitherto his meal ticket, is now forced to exert itself mechanically under duress.

The menage a trois at the end of Entertaining Mr Sloane is as clinically neat and logical as that created at the end of Design for Living, while differing from it in being puckishly punitive. But if Coward's play stands apart from all these other examples in the impunity and symmetrical thoroughness with which it recommends the three-cornered solution, this may be because it is depicting a special class of people - stars like Fontanne, Coward and Lunt who played Gilda, Otto and Leo - and that the title is meant to be ironic. In his autobiography, Coward reveals that early on in their careers, he, Fontanne and Lunt had made a pact that 'when all three of us had become stars of sufficient magnitude . . . then, poised serenely upon that enviable plane of achievement, we would meet and act triumphantly'. Their path to creating Design for Living thus revealingly mirrors the path of the three characters to their menages, for it's a peculiarity of the play that the main obstacle to the triangle is not problems of conscience or sexuality, or even the jealousies caused by the trial pairings, but the fact that the three of them aren't equally successful at the start. It's only when each has gone off and achieved fame (as artist, playwright and interior designer) that they are able to unite as a threesome.

In the famous photograph, reproduced here, from the first production of the final scene, Coward and his co-stars are intertwined on a sofa and laughing with callous glee at the prat-falling exit of Ernest, Gilda's well-named art-dealing husband who, as he's forced to storm out of his own flat, trips over a package of canvasses. The image is one of exclusivity, of an irresponsible elite closing ranks against the dull and respectable, a fact to which contemporary skittish allusions to the play were alert, as in this sketch where Bert Lahr and Ray Bolger sang 'We're living in the smart upper sets / Let other lovers sing their duets / Duets are made by the bourgeoisie - oh, / But only God can make a trio.'

As Sean Mathias notes, the central relationship is so much a matter of preening self-display that 'they can hardly bear to be alone together'. It will be fascinating to see whether a director as good as he, using actors chosen for their non-Coward qualities, can give the play sex as well as stage-struckness and make it work as a design for living that non-members of Equity might consider. On the face of it, Coward's triangle triumphs, where all else fail, largely because this menages a trois is an egoisme a trois as well.

'Design for Living' is at the Donmar Warehouse, London WC2, until 5 Nov (Booking: 071-867 1150)

(Photograph omitted)