Waiting for Godot, Theatre Royal, Haymarket, London

Sewer-rat, curate, cretin... critic!" Vladimir and Estragon do nothing but talk dirty to one another for two hours in a play once described as the one where nothing happens, twice. But as Beckett's tramps are played by Patrick Stewart and Ian McKellen – renewing an old association going back through the X-Men films to the RSC 40 years ago – the banter and the bitchiness has an added sting.

These really are two old has-beens who might-have-been fifty years ago, repeating an old routine within a plaster false proscenium on a sloping platform of boards, with a stage trap where Godot's transfigured messenger boy appears with not much news and Simon Callow's bulbous Pozzo interrupts a double act blathering about zilch.

Sean Mathias's Haymarket production redefines the vaudeville in the trans-Pennine shuffle of Boltonian McKellen and West Yorkshire Stewart. Stewart's Vladimir is restrained and accommodating, slightly daunted by the idea that he's on the stage at all in order to give the impression that he exists. He plays second fiddle and seems pretty happy about it.

McKellen acts his boots off as Estragon – but never seems hampered by his trademark mannerisms or intonations. His huge hams of hands are eloquently deployed and his big rheumy eyes rake the void without beseeching our sympathy or cheap laughter.

It's a wonderful double act, combining the old world dignity of Alan Howard and Ben Kingsley 10 years ago and the low vulgarity of Max Wall and Trevor Peacock even further back.

Ronald Pickup's Lucky, long-haired and remaindered like Ben Gunn, is a beautiful repository of old memories, an enslaved partner while Vladimir and Estragon shuffle in the outer room of what could be an audition process. Is Godot a casting agent after all?

Godot is 55 years old now, and it's impossible to think that anyone might find it obscure, though it still seems like a play that cannot make up its mind in the battle between philosophy and religion. The truth is, it's about both, and the wonderful humanity of Stewart and McKellen ensures that you never think for one minute that they are talking nonsense. Or at least, it's nonsense we don't mind listening to.

To 28 June (0845 481 1870)