“Human life is so fragile”, Rosamund Pike’s Marie Colvin tells us at some point in grisly biopic A Private War. When Colvin says it, we listen; a war reporter on the foreign desk at the Sunday Times, her two-decade run of assignments – in Srebrenica, Sri Lanka, Libya, Syria – serve as a kind of sick knockout phase in a tournament of global conflicts.

The story is unabashedly Colvin’s but the fact finder in this particular tale is Matthew Heineman, the documentary filmmaker who makes his feature debut. His film is another chapter in a lengthy, expanding book on journalistic nobility, but it sticks out for its grit and a dogged commitment to reality.

The complexity of Colvin in A Private War, however, is disappointingly Freudian and, dare I say, overly typical of a surface-level British psychological study. Ultimately, the straightforward archetype of “woman who can’t switch off”, troubled by bad habits and some vague trauma, is all we really get. There’s more nuance in an episode of Homeland, where Clare Danes does much the same thing.

Even in her solid performance, too, Rosamund Pike represents a missed opportunity to have casted more boldly. When Colvin is the rugged, flippant American in a room of British bow-tie wearers – she even wears an eye patch – Pike’s fresh-faced Anglicism escapes its brief repressions. You get the sense an American actress might have achieved a similar austerity with half the exertion, and economised elsewhere.

Related to this is the setting of A Private War, genuinely remarkable as an unglamorous portrait of the journalism world. That doesn’t mean the film is better for it. In truth it isn’t abundantly clear quite why Marie Colvin does it, and so it becomes difficult to care too deeply for the fact that she does. This might be a central problem of telling history so soon after the event, and while so many of the central figures are still alive. But the film doesn’t gain from it.

The supporting cast is similarly logical, but unexceptional. Tom Hollander returns as his usual exasperated, fraying bureaucrat, similar to a role he played exceptionally in “In The Loop” and, more recently, “Bohemian Rhapsody.” But in such a humourless film, we know he can do better. Jamie Dornan as Colvin’s trusty photographer Paul Conroy, and Stanley Tucci as a painfully underdeveloped love interest are, likewise, competent and much too conventional.

The central problem, however, is Heineman’s failure to lend a singular look to his film. The camera meanders from dynamic, handheld scenes to expansive panoramas; like Colvin, A Private War has trouble settling. For the first hour or so this is acceptable, but as the plot becomes increasingly consequential and the scenes heavier in tone, the audience is within reason to expect visual coherence. Unnecessarily elaborate set-ups and then claustrophobic sequences never seem to mesh well together.

Though the lessons Heineman learnt making documentary films haven’t gone unnoticed, and the scenes of intensive conflict are superior to most in the genre. When the digging of a Fallujah mass grave can only bring up rock and bone, the gut-punch is in the fact we can barely tell the difference.

A Private War, however, never manages to take hold of its narrative. As with most biographical films of decent quality, the powerful scenes are the truthful ones. A CNN interview in a Syria hideout collapsing around her is a dramatic highlight, but still fails to move far beyond the brutal reality of the film’s central arc, to which Colvin dedicates her life. An incisive documentary would lose out on these crumbs of dramatic tension. But it could also have done a better job telling the tale.