THEATRE / Virtual reality: Paul Taylor on electronic circuits and electric performances in Ninagawa's production of Peer Gynt at the Barbican; plus Thomas Otway revived in Manchester

Captivating large audiences seems to come as naturally as breathing to Michael Sheen - which is just as well because in Ninagawa's vast, multi-national Peer Gynt, now at the Barbican, the mop-haired 25-year-old Welsh actor has to hold the stage for more than four hours, taking Ibsen's incorrigible fantasist and liar from impetuous youth to the dark disillusions of old age.

Directors often divide the responsibilities of the part between two actors. Peter Stein employed six, a job- share relay that emphasised the onion- like corelessness of the self Peer pursues in his circular quest. Ninagawa's questionable conception of the play firmly dictates, however, that the whole role be performed by one young person.

His version begins and ends amidst the flashing electronics of a modern games parlour. Standing dreamily apart from the other machine-addicted youths, the boy who becomes Ibsen's hero is imagined as entering the world of virtual reality, sucked into the software that sends him on Peer's journey through life - a vicarious experience of truly epic proportions.

Given that the many virtues of the production seem to me to be almost entirely independent of this over-arching design, I'll try to state the problems it poses briefly. One is that, even if the concept were desirable, it isn't given enough theatrical substance. The computer graphics of orbiting onions and destinationless journeys that are flashed on a scrim between the acts, and the electronic circuit on the surrounding walls, are curiously inert and ineffective as reminders that this isn't supposed to be a brilliant but conventional piece of theatre.

More harmfully, the dangling implication that Peer's adventures are somehow provisional, technology-generated experiences increases the difficulties any young actor (even one as gifted as Sheen) would encounter in projecting the pain and the scorching sense of futility of embittered old age. How can its tragedy properly register if the process is so manifestly reversible, just a matter of removing the grey wig and beard and re-emerging as a now flukily wised-up kid?

Why then is the production compulsory viewing? One reason, as you might expect from this director, is the matchless painting with light. How characteristic that he should, for example, depict the ectoplasmic, maddeningly ungraspable Boyg as a maze of luminous spots that keep dancing into new positions. Another is the attractive energy and versatility of the predominantly young, predominantly Irish cast, in which such actors as Michael Fitzgerald pull off extraordinary acid-etched doubles - a quietly barking lunatic one minute, a comically suave and insouciant Strange Passenger the next.

Mainly, though, you'd be a fool to miss Sheen who takes to a large stage like a school of dolphins takes to the ocean. He has all the equipment to be a great actor: instinctive presence; the ambiguity of delicacy / roughness, male / female in that odd clown / angel / urchin face; the capacity to make tragedy and comedy happen simultaneously; and an indestructible voice. In Anglophone middle-age, his Peer leans a bit heavily on caricature, but his layered portrayal of the exuberant yet insecure Welsh boyo of the first three acts manages to combine winning exhibitionism with a streak of evasive defensiveness and self-deception that invites a more complex response.

In the scenes with his mother (the excellent Paola Dionisotti) and with Catherine White's delightful Solveig, Sheen's Peer shows you how a career of letting yourself off the hook can be a paradoxically painful business. I'd want to single out, though, his wonderful reaction to watching the youth who cuts his finger off to avoid being called up. The compulsive dreamer is mystified by the doer and Sheen, in his quietly chastened reflection on a type of being from which he is excluded, makes you think of Hamlet contemplating Fortinbras. The day when he plays the Dane can't be far off. In the meantime, this autumn, he tackles the next best thing, Konstantin, Chekhov's complicated Hamlet manque.

At the Barbican (071-638 8891)