In the 1920s, the Marlowe Society at Cambridge and the Old Vic mounted productions that played to houses consisting largely of First World War veterans whose experiences at the Front would have sensitised them to appreciate Shakespeare's bitterly cynical demythologising of that great ur-conflict, the Trojan War, and its pantheon of emblematic heroes.
From these belated beginnings, the play has gone on to provide a century that has been unfancifully described as the worst 100 years in the history of the human race with a prime theatrical parallel for ignominious international conflicts ranging from post-war Berlin and Vietnam to Northern Ireland and Bosnia. The last decade has seen a positive glut of English productions from Sam Mendes's superbly eclectic 1990 RSC production at the Swan - which, like Eliot's The Waste Land, seemed to be elapsing in a number of time schemes simultaneously - through Ian Judge's strenuously homoerotic mid-Nineties staging (known as A Thong for Europe by its friends), down to an intelligent production by Alan Strachan last summer in, of all places, the Open Air Theatre in Regent's Park. When a prickly uncompromisingly intellectual play like Troilus finds a home in that sylvan centre of bourgeois self-satisfaction, you know that it has decisively entered the mainstream.
With the last year of the millennium about to offer us two major new stagings of the piece - from Trevor Nunn, whose version opens next week in the Olivier, and Dominic Dromgoole, whose production for Oxford Stage Company will tour 2,000-seater theatres in the autumn before possibly coming to the West End - this is an auspicious moment to ask whether its provocativeness is in danger of getting lost beneath our new-found familiarity with the play.
Consider the RSC's current staging by Michael Boyd. It shifts the action to the Irish civil war of the 1920s (the Trojans are the Irish in a shelled Catholic chapel; the Greeks are British) but in such a dutiful, undriven way that you sit in front of it calmly nit-picking and finding holes in the parallels (how can a play which turns so much on the idea of single combat survive in a world of pistols? etc). Can we really have become blase about this masterpiece?
From their quite different angles, Nunn and Dromgoole would be tempted to answer in the affirmative, and both have plans to deal with the problem. A seasoned thirtysomething veteran of the new-writing scene (at the Bush, which he ran, and at Peter Hall's Old Vic), Dromgoole, now installed as OSC chief, reveals that for him, the eerie modernity of the play lies less in its anti-heroic debunking of war (the rigged lottery, the shamelessly self-serving casuistry of the great debates etc) than in something he describes as "a sort of lapsed or slipped reality within it. There's a very contemporary disturbance about perception and what is real - just as there is in, say, Michael Frayn's Copenhagen."
He points to the great sequence where Troilus and Ulysses spy upon Cressida's treacherous tryst with Diomedes and Thersites, the scabrous camp follower, slaveringly spies on the spies. What is frightening and modern here is the lack of any hierarchy in the clashing perspective on what is seen and the wild philosophical extremity of Troilus's wounded response: "This is, and is not, Cressid."
In the earlier scene where the lovers make their desperately ironic vows, Cressida refers to a future "When time is old and hath forgot itself", likening its forthcoming self to someone gone gaga with age. But, if not precisely senile, time in the play is certainly old way beyond its years.
There's a peculiar tart tension in this drama between a sense of (as Dromgoole puts it) "men making up their own myth as they go along" and of heroes acting in the half-conscious light of posterity's press releases about them. We hear that, in their tent, Patroclus is entertaining Achilles with a pageant of irreverent impersonations of the other Greek luminaries. The self-reflexive effect of this - Patroclus's performance mirroring, in miniature, any performance of Troilus and Cressida - is of a hand suddenly bursting through a classical painting in a gallery and pointing directly at the startled onlooker.
And this teasing traffic between the play's present tense and the foreknown future serves merely to heighten those extraordinary moments when the play seems to have premonitions of 20th-century existentialism, as in the pregnantly pinpoint focus of Agamemnon's greeting of Hector: "What's past and what's to come is strewed with husks/And formless ruin of oblivion/But in this extant moment..."
Dromgoole is toying with the idea of a contemporary setting, the characters transposed to the underclass: "there's a great Mike Nichols quote that all the primal patterns and paradigms come from either the upper class or the underclass. I think Troilus is a story you can relate to the urban myths of the underclass." He dislikes over-specific modern parallels, such as Bosnia, because "it seems like appropriating other people's tragedy". So does Trevor Nunn, though for broader reasons.
His production, which will pit black Trojans against white Greeks, is set in the Homeric world. "The problem when you update," argues this great Shakespearean director (the only man to have made Macbeth work, and work brilliantly, on the modern stage) is that, at a stroke, you remove the sense that these people are struggling with issues for the first time. You've got to the end before you've even started."
He aims to stress the development in the play from the relatively chivalric and uneasily conscious-riven to the despairingly cynical and nihilistic, with "a random act of war" (a political exchange that involves Cressida being returned to her traitor father) as the watershed event.
The drama's tone of voice alters, he contends. "Thersites grows in influence as Pandarus [the lovers' campy go-between] wanes." Nunn is alive to the competing levels of reality in Troilus, but feels that the accent should fall on that aspect of the characters which remains in ignorance of their future and unself-conscious about their dramatic function. "There's a wonderful irony in the scene where Ulysses prophesies the Fall of Troy and Hector says `I must not believe you... The end crowns all/And that old common arbitrator, Time,/Will one day end it'. Now, we know, as they speak, the outcome and the almost limitless number of tragedies that developed from that point. The speakers do not, and there's something absolutely thrilling about that. And it's as effective now as it was for the play's first audiences."
Between us and those first audiences, though, lie a lot of knowingly jokey, but much less radical attempts to link the mythic and the modern - from, say, the barbed, flippant operettas of Offenbach (La Belle Helene, Orphee aux Enfers) in which French Second Empire society mocked itself in terms of an Asterix-like classical world, through to the helicopters and Kissinger-like Julius Caesar in Howard Brenton's The Romans in Britain.
TV monitors spewed up contemporary televisual images at the start of The Vertical Line, John Berger and Simon McBurney's recent site-specific piece in the Underground, as a debriefing preface to a journey downwards and backwards to the paradoxically much fiercer modernity of the earliest cave paintings known to man. Perhaps it is only through a similar bombardment in the theatre's foyers (cue Offenbach and Up Pompeii footage) that a contemporary production can do full justice to the sense that, even at the millennium's end, Troilus and Cressida is a play which in its pre- emptive, destabilising astringency, continues to anticipate us.
The National's production is in rep at the Olivier (0171-452 3000); the RSC production is on tour (01789 205301) to 5 Jun