The Reporter, Cottesloe, National Theatre, London

Before he took his own life in 1971, the reporter James Mossman wrote a cryptic suicide note: “I can’t bear it any more, though I don’t know what ‘it’ is.”

The neat idea behind Nicholas Wright’s new play is that Mossman conducts an inquiry into what “it” is. So Mossman examines his own life with the same forensic zeal he brought to foreign reporting and fronting Panorama.

It is a bogus quest, of course – from the outset we are pretty sure that Mossman will not pin down one sole reason for his despair. But the chase enables Wright to explore both the slippery nature of truth and the elusive nature of personality. And the whole piece is charged with irony, as it is presented with the authoritative, apparent objectivity of a TV documentary. The friction between the dry, detached style and the pliant, painful truth drives the evening. The peeling away of layers, onion-like, to arrive at no solid centre is essential to the play’s point – but the downside is that it limits it as satisfying drama.

Mossman, played with a mesmerising mix of charisma, cool reserve and intense, coiled energy by Ben Chaplin, conducts us through key moments in his life. He sets aside his early spying career as irrelevant and begins in 1963, with his personal witness of the Buddhist monk incinerating himself in Vietnam. It is here that he first sees a rift between horror and the reporting of horror. Other ports of call include his acerbic grilling of Harold Wilson on Panorama and subsequent difficulties at the BBC, his tempestuous relationship with his mentally unstable male lover and his curious friendship with the novelist Rosamond Lehmann. Mossman emerges as a man ahead of his time in his profession and deeply disillusioned by it, trapped between deep feelings and the expediency of reserve.

The dry wit of Wright’s style and the detective nature of the quest make the play never less than absorbing. And Richard Eyre’s production combines a seductive, brooding atmosphere with wonderful comic details. Yet the piece also frustrates. It does not give enough substance to Mossman’s reputation for brilliance, and its episodic structure means that characters are not fleshed out, that we only get a snapshot of important events, that the focus keeps moving on. This is presumably part of the point – but it can’t help but limit its impact dramatically. ★★★☆☆ Tel 20 7452 3000