Now that its influence has begun to wane, and it ceases to remind us of its imitations, we can again see the most influential play of the second half of the 20th century for what it is. Waiting for Godot has lost none of its power to astonish and to move, but it no longer seems self-consciously experimental or obscure, writes actor and author Simon Callow, 50 years after its first English-language production

With unerring economy and surgical precision, the play puts the human animal on stage in all his naked loneliness. Like the absolute masterpiece it is, it seems to speak directly to us, to our lives, to our situation, while at the same time appearing to belong to a distant, perhaps a non-existent, past.

In his subsequent plays, Beckett created a number of ineradicable images of the human condition, but it is his first performed play, which had its English-language premiere in London 50 years ago this year, that has joined the select stock of myths by which we understand ourselves.

That Samuel Beckett should have chosen to write a play at all is something of a mystery. "You ask me for my ideas on Waiting for Godot and my ideas on the theatre," he wrote to Michel Polac on Godot's publication a year before it was produced. "I have no ideas on the theatre. I know nothing about it. I never go. That's reasonable. What is rather less so," he added, "is . . . to write a play, and then to have no ideas on that either."

Despite a youthful fondness for the art theatre in his native Dublin, and for the variety theatre anywhere, he was no buff, and his writing up to this point, inspired by the example of his literary masters, James Joyce and Marcel Proust, had consisted of fiercely difficult novels, poems and short stories. True, in 1930, he had written Whoroscope, a verse monologue in the voice of Rene Descartes, but it was never intended for performance.

After 1940, his work had undergone a radical change. If he was to write about impotence and ignorance, which he now conceived to be the essential experience of human life, he must, he said, abandon rhetoric and virtuosity. The English language having a natural propensity for both of these, he abandoned it, henceforward writing in clean and analytical French, swiftly writing three great novels, Molly, Malone Dies and The Unnameable, in his adopted language, each of which is in the form of a soliloquy; none of them knew any immediate success and, indeed, it was almost impossible to find publishers for them. His decision to write for the theatre was, Lawrence Graver acutely notes, a part of this stripping away: in doing so, he eliminates the voice of the narrator.

It seems that it was also partially the lure of immediate returns, however modest, from the box office that suggested to the impoverished Beckett that he might write plays. His first was Eleutheria, a clumsy and over-ambitious experiment full of prefigurings of later Beckett - the hero is called Krapp - which he immediately followed with Godot, in which his touch is infallible.

The two plays were touted around unsuccessfully until Beckett's friend Suzanne Deschevaux-Dumesnil took them to a progressive actor-director, Artaud's associate Roger Blin, who plumped for Godot because it had only five actors and one tree.

Characteristically, Beckett was delighted to find that Blin's current production was playing to half-empty houses: a guarantee of integrity.

It took two years for Blin to raise the money and get a theatre; finally, when the play opened in January 1953 at the nearly defunct Theatre de Babylone in Montparnasse, it was greeted with a mixture of critical bewilderment, a certain amount of active audience hostility, partisan enthusiasm from some highly influential quarters (Jean Anouilh, the most successful French dramatist of the day, called it the most important theatrical premiere in 40 years) and straightforward delight from the paying audience, who attended the show in ever-growing numbers. It was word of mouth that swung it.

This curious paradox - the play's ability to frustrate intellectual criticism with its apparent elusiveness, while gripping with a vice-like hold those who neither know nor particularly want to know what the play means - was repeated in London and on Broadway.

It is a remarkable fact that both in America and in England, commercial managers were keen to do the play; the problem in the UK was that none of the great actors approached would commit to it. Ralph Richardson was among them; he reproached himself for the rest of his life for turning down "the greatest play of my generation".

Instead, the young Peter Hall cannily picked the play up, doing it at his Arts Theatre with an unstarry cast. The overnight reviews were dismissive, whereupon the great play agent Peggy Ramsay, using the guerrilla tactics for which she was famous, persuaded Hall to send Harold Hobson, the powerful critic of the Sunday Times, a copy of Beckett's novel Watt before he wrote his review. The result was a panegyric; business built and eventually a successful West End transfer ensued. Hall is currently directing a 50th anniversary production at the Theatre Royal, Bath.

Of course, the play did not appeal to everyone: Peter Bull, the first English Pozzo, recollected a matinee at which an elderly lady penetratingly observed to her companion in the fairly wide open spaces of the stalls: "I wish the fat one would go." But, by instinctive genius, the tyro playwright had produced a work of absolute originality which was so sure-footed in its theatrical sense that, despite defying all contemporary expectations, it communicated effortlessly with audiences, distilling its truth with the simplicity and profundity of a great poet who was also a sublime humorist.

Beckett's informed love of the great vaudevillians - especially Laurel & Hardy and Chaplin - enabled him to produce a work which stirs the heart of anyone who has been moved to laughter or tears by clowns, existing as they do in the tension between the dread of being alone and the horror of dependency. Eric Bentley remarked of the first New York production that "highbrow writers have been enthusiastic about clowns and vaudeville for decades, but this impresses me as the first time that anything has successfully been done about the matter".

Of course, it helps if the actors playing Vladimir and Estragon are great clowns or vaudevillians themselves. Bentley saw Bert Lahr - the Cowardly Lion from The Wizard of Oz - in the role of Estragon. "The perfect execution," he said, "by a lowbrow actor of a highbrow writer's intentions"; 20 years later, in Manchester and London, Max Wall performed the same service.

But such casting is a luxury; the play's opening image, of a tramp/clown in his bowler hat, tugging at his boots, with a solitary tree behind him, shortly joined by his identically attired comrade, creates the sort of deeply stirring emotion that the first sight of a great clown produces.

These men - like all the great theatre images: Mother Courage with her cart; blind Lear; Falstaff wrapped around Doll Tearsheet - come from our dreams, from deep in our unconscious memories. We are them; they are us.

There is indeed a good case for thinking of the play as a dream play in its repetitiveness, its circularity, its sudden absurdities, its arbitrariness and savage eruptions. Estragon can barely keep awake, and sleep is a blessed state because the sleeper is oblivious of life's terrible reality: "He is sleeping. He knows nothing. Let him sleep on."

The characters themselves seem to shift shape oneirically: out of the blue, Vladimir becomes an eloquent philosopher, quoting Latin tags; Estragon announces that "we are not caryatids"; for no known reason Pozzo is suddenly blind, Lucky suddenly dumb. An uneasy sense of unreality pervades everything: "You're sure you saw me?" Vladimir asks the boy. "You won't come back tomorrow and say you never saw me?"

Just as in Strindberg's Dream Play, where Agnes's repeated cries of "Poor, suffering mankind!" pierce the action, Didi and Gogo constantly cry out, apropos of nothing in particular, "What'll we do?! What'll we do?!" But perhaps the dream is just the dream of theatre. Beckett's play is as conscious of its own theatricality as any by Brecht, by Pirandello, or - the comparison is inevitable and apt - Shakespeare.

Theatrical imagery pervades the play. Vladimir, shocked at Pozzo's treatment of Lucky, accuses him of chucking him away "like a . . . like a banana skin", to be stepped on, no doubt; when Pozzo delivers one of his lectures, he sprays his throat like an opera singer or a boulevard star; Vladimir and Estragon play-act to fill the void, doing old routines with hats; Vladimir takes on the role of Lucky, putting on his hat and walking up and down like a mannequin; when Estragon is terrified of being beaten up, Vladimir pushes him towards the auditorium: "There! Not a soul in sight! Off you go." Estragon recoils in horror, dreading the idea of becoming part of the audience, a fate worse than death.

Even the twilight itself is, according to Vladimir, "nearing the end of its repertory". Instantly, Beckett, in his first performed play, understood every possibility of the theatre as metaphor. Slyly self-referential, he gives his tramps an exchange in which they say: "Charming evening we're having." "Unforgettable." "And it's not over." "Apparently not." "It's only beginning." "It's awful."

His characters are as much of a mystery to Beckett as they are to us; that gives them a great part of their fascination. They are archetypes, who have emerged, ancient and novel, from tradition. No doubt, as James Knowlson perceptively observes, Beckett coloured their situation with his own wartime experience of living in the sticks, in Roussillon, waiting, waiting for the war to end before life could begin again. No doubt Pozzo has qualities of the concentration camp capo. But the characters' existence is beyond history, beyond logic.

"I know no more about this play than anyone who just reads it attentively," Beckett wrote. "I don't know what spirit I wrote it in. I know no more about the characters than what they say, what they do and what happens to them . . . everything I have been able to learn, I have shown. It's not a great deal. But it's enough for me, quite enough. I'd go so far as to say that I would have been content with less . . . Estragon, Vladimir, Pozzo, Lucky - I have only been able to know them a little, from far off, out of a need to understand them. They owe you some explanations, perhaps. Let them unravel. Without me. Them and Me, we're quits." - Guardian Service