Caligula, Donmar Warehouse

In showbiz terms, what does the name Caligula mean to you? Probably either the cracked and cackling John Hurt in I, Claudius or that toga party from hell in the notorious Bob Guccione Penthouse movie, starring Malcolm McDowell, a bummer from which everyone, starting with Gore Vidal, fought in vain to dissociate themselves.

As far as popular culture goes, it's a name more associated with sex and scandal than with philosophy. A metaphysical project is the underlying aim, though, of his mad reign of terror in Camus' play Caligula, which is revived now in Michael Grandage's savagely funny and superbly judged production at the Donmar Warehouse. It uses a zestful and fresh-sounding new translation by David Greig.

The play homes in on the young Roman Emperor at the point where the death of his incestuously beloved sister, Drusilla, has brought about a life-changing existentialist conversion in him. If the world is essentially absurd and meaningless, he reasons, why is one action any better than another? Society, which represses this truth, needs to be undeluded and taught a lesson. And who better to achieve this than a man with absolute power; and how better to do it than by a regime of arbitrary hedonism and violence?

In a role that could easily become rebarbative and repetitive, Michael Sheen gives one of the most thrilling and searching performances I have ever witnessed. At the start, he beautifully establishes the dazed, groping sincerity of Caligula's born-again predicament. Whether dolled-up as an eye-batting drag Venus in a blasphemous travesty or blowing the whistle on bad poets in a hilarious Gong Show-style verse contest, Sheen shows you an agonised young man who is genuinely trying to grapple with the intellectual conundrum of why there should be morality at all.

Sheen, with his triangular, sensitive-clown's face and his physical flamboyance is dream casting. He and Jason Hughes, the actor who plays his Roman sidekick here, were Jimmy Porter and his sidekick Cliff in an excellent recent production of Look Back In Anger at the National.

On the evidence of this, Sheen would make a stunning Hamlet and Grandage would be the ideal director. Come on, guys, what are you waiting for?