Beneath the branding, the Barbican is only indulging in what virtually every other cultural institution and certainly every conceivable branch of the media is doing. We are up to our eyes in millennial stocktaking, succumbing to fin-de-siecle fever. Portentous lists of The Century's Best are being busily compiled and the latest contender in the ring is the National Theatre which has launched NT2000, a celebration of the most "significant" plays of the century. The deadline for submissions is now past and all we have to do is wait for the results of the poll of 800 writers, actors, directors, designers, academics, administrators, critics, commentators and politicians who have been asked to cite 10 plays and, in an echo of Desert Island Discs, to answer the question: "And if you could only have one...?"
The most important question in such compilations is not which work comes out on top, but rather, how do you define your terms? As with all surveys and statistical pile-ups, the truth lies in the methodology. The National initially sets out its stall very strictly. The plays must be written in English or translated by the author. That means we can pick works Beckett originally wrote in French but not Chekhov's masterpiece The Cherry Orchard which for many, myself included, is the play of the century.
It also banishes Brecht and Pirandello, without whom acres of the dramatic repertoire of the second half of the century would have been inconceivable up to and including Stephen Sondheim. Sondheim has often announced his dislike of Brecht but the interplay of distance and emotional engagement in his own work is completely indebted to Brechtian techniques.
Not that Sondheim's work is up for consideration. Musicals have been barred. This is largely due to practical reasons, as the votes cast will result in a list of 100 plays being presented in a year-long series of 45-minute platform events, each one highlighted with discussions and excerpts. Presenting musicals in this fashion is impossibly expensive and you are faced with the problem of collaboration. In the majority of cases it is the music which makes them great, which means lauding composers rather than writers.
Clearly, the intended emphasis is on dramatic literature. Unfortunately, the National then muddies the waters. Recognising the subjective nature of it all, the small print allows us to choose plays that represent a genre, a period of history, or reflect popular choice. The last of these means we should probably have to opt for The Mousetrap which has, after all, been running for nearly half the period under discussion. Worst of all, we're encouraged to include "simply plays that you have enjoyed".
Given that most people cannot distinguish between performance, direction and text, this opens the door to hugely enjoyable productions of second- rate plays in which, say, a stellar performance blinded audiences to weaknesses in the writing (Judi Dench in Amy's View?), which is surely missing the point. Of course the yardstick of enjoyment is important but it panders dangerously to the intellectually lazy notion that "what I like" is the same as "what is good". Whatever happened to objectivity? Thus critical rigour goes out the window and the term "significant" is reduced to a state of meaninglessness.
Yet even if one adheres strictly to the criterion of "significance", what does that mean? The National suggests that the word be used in the sense of "great, influential or important". Larry Kramer's Aids clarion call The Normal Heart was massively significant in social and political terms but although it made for powerful theatre, by no stretch of the imagination is it a great play.
It is more useful to see "influential" as applying to not only the imagination and emotions of audiences but to the evolution of theatre itself. This means that John Osborne's Look Back in Anger is a dead-cert for inclusion. The first "kitchen sink drama", it sent shock-waves through the theatrical establishment in 1956. Revivals have revealed, however, that although the writing for the central character Jimmy Porter created a massively influential new voice in every sense, the play as a whole is unbalanced, overwritten, misogynist and deeply sentimental.
Nor is it Osborne's best, a point which leads us to the crux of the matter. Samuel Beckett's Waiting for Godot is, without doubt, the century's single most influential play. It redefined almost every rule of plot, character and structure but it was just the beginning of Beckett's journey. His compelling syntheses of theatrical image and metaphor grew purer and more intensely dramatic as his career progressed. Play (1963), Not I (1973), and Footfalls (1976), to name but three, are finer, more dramatically distilled works.
It is the same story with Harold Pinter. His first full-length play The Birthday Party (a miserable flop in 1958) heralded a sea-change in the construction of dialogue and the rendering of theatrical "realism", and that is just for starters. It was early days for a talent that flowered further with The Homecoming (1965) and reached maturity with the fully achieved and astonishingly fluid Old Times (1971) or the magnificent Betrayal (1978).
The game would be altogether easier if one were being asked to name the century's greatest playwrights, about whom there is surprisingly little dissension. The problem here is that greatness, removed from the excitement of fashion, needs time to reveal itself. The closer one gets to the present, the harder it is to assess the importance and resonance of a particular play. With a dead playwright, all one has to do is to select the finest, most mature expression of his or her ambition and achievement, but the untested nature of recent judgements means that younger writers get a raw deal. Tony Kushner's Angels in America or Phyllis Nagy's Never Land may turn out to be massively influential, but who can tell?
The final problem is partial knowledge. All sorts of circumstances lead one to describe a play as so-and-so's best, not least of which is having seen key works in either good or bad productions. My favourite David Mamet play is Sexual Perversity in Chicago but deep down I know that American Buffalo is better but unlike the former, I have yet to see a truly outstanding revival of it to convince me. Conversely, to my shame, I don't know how to place Harley Granville-Barker, an important playwright from the early 1900s, most of whose work I have never seen.
However you strive for objective analysis, personal bias creeps in. Not to mention lies. As with sex surveys, some people will undoubtedly select plays that put themselves in a good light or recommend the work of colleagues. So with my apologies to ghastly omissions like Bernard Shaw, Terence Rattigan, Edward Albee, Joe Orton, David Mamet and all your favourites, here is my utterly impartial list in chronological order.
Private Lives (1930): Noel Coward's most perfectly constructed play. A bewitching marital comedy of passion and denial whose surface laughter is built upon extraordinary emotional depth.
A Long Day's Journey Into Night (1940): Eugene O'Neill's self-lacerating family drama has a unique rhythm and a compelling cumulative power.
A Streetcar Named Desire (1947:) Tennessee Williams's vividly atmospheric, lyrical masterpiece.
The Crucible (1953): Arthur Miller's flawed but dramatically gripping allegory of McCarthyism set during the Salem witch-trials.
Saved (1965): Edward Bond's play caused one of theatre's most notorious scandals for the scene in which a baby is stoned to death in a pram. All of which obscured the power of his vision, the economy and compression of his dramatic language and - an essential criterion - the compassion of the writing.
Not I (1973): Samuel Beckett's searingly beautiful depiction of humanity through the mouth of a woman. A truly unforgettable piece of dramatic writing
The Norman Conquests (1973): Alan Ayckbourn's brilliantly interwoven comic trilogy grows in depth and complexity before your very eyes, is minutely observed and, frankly, hilarious.
Betrayal (1979): Harold Pinter's elegiac story of a love triangle played in reverse is so assured that even people who think they don't like or "get" Pinter fall under its heartbreaking spell.
Racing Demon (1990): David Hare's masterpiece is a superbly layered state-of-the-nation play using plots within the Church of England hierarchy to illuminate ideas of faith with a rare breadth of sympathy.
And, finally, my play of the century:
Top Girls (1982): Caryl Churchill's stunningly moving study of the enticements of power and the contradictions we are forced to face was groundbreaking in its reworking of the basic dramatic rules governing time, manner and place. It was also utterly alive to the world in which she was writing and remains so today.