Light can be elusive. Not the kind you switch on, but that which appears of its own volition. The stuff that, in this madcap comedy about a film crew, Matt Smith's movie director Maxim yearns to capture; the kind that can change a mood, create an atmosphere or, in a fleeting moment even evoke the eternal answer to the meaning of life, as Maxim puts it.

And true enough, in the final flourish of Anthony Neilson's production, many of these qualities are evoked in a way that feels truly profound.

Or, rather, it would if this play were not entirely populated by a bunch of complete narcissists.

Maxim's childish tantrums, and his crude attempts at attracting sympathy by pretending he has asthma is not the half of it. His producer (Amanda Drew) treats her cinematographer lover (Richard Pyros) like an unpaid male prostitute, though his behaviour is no less self-serving when he encourages the sacking of Maxim so that he can take over as director. All are as selfless as Gandhi, however, next to Jonjo O'Neill's grotesque Hungarian film star.

Think of the German actor Klaus Kinski - half artist, half psychopath - and you won't be too far from the epic vanity of O'Neill's version of this archetype - a violent, loose-cannon prone to expressions of grandiosity and self-sacrifice all bound up in a messiah complex bigger than Jesus's.

All this is terrific fun to watch, and there's no doubting the talent of the cast and director/creator whose previous works about the human psyche have proved that Neilson has one of the more fertile and febrile imaginations at work in the theatre. But the play, devised in the rehearsal room, gives its cast licence to corpse at their own hilarity, and ad-lib. They do this apparently unaware that they are indulging in the kind of narcissism their show is intended to parody. Most fatal of all is that the story has no significance beyond its own characters. Smith - surely the most watchable Dr Who of recent times - almost manages to be likeable.

But there is a sense here that everyone involved is reaching for something deeper and more enriching, qualities that prove as elusive as a certain kind of light.