Richard Jobson’s The Somnambulists, shot earlier this year, takes its inspiration from an eponymous 2008 exhibition of photographs by Joanna Kane in Edinburgh. At first glance the portraits seemed to depict a series of sleeping people, but turned out to be death masks. The film, which shows 15 British servicemen and women who served in Basra in Iraq telling their stories, creates a similar haunting impression.

Played by a cast of unknown actors, who voice the testimonies gathered from real life soldiers, they emerge from the dark one by one to deliver their monologues, like Shakespearean actors. You only see their heads, seemingly floating in space, forcing you to focus on the words and the faces, although I couldn’t help wondering what had happened to their bodies. Had they lost limbs?

Most are regular soldiers, but there are also a bomb disposal expert, a sniper, two medics, a commanding officer. Most of them are young, and several recount that they joined the army simply because they couldn’t get a job. One young black female medic says she wanted to be a doctor but her family couldn’t afford to pay for her medical training while the army offered it for free.

Basra was hell, most agree, apart from one chap who loved the camaraderie and the sense of belonging to a community which he’d never experienced before. Unlike many of the others who have been worn down by the daily roadside bombs and other attacks (“contacts” in military speak), he doesn’t hate the Iraqis. “What if they had liberated us from Tony Blair?” he asks, eliciting a rare laugh from the audience.

By contrast, another does not remember any camaraderie. When he returned from a particularly bloody patrol, everyone was shouting his name. It turns out his fellow soldiers had taken bets on him, making him the favourite not to return.

Another recounts how his partner made him vote Labour because she thought Tony Blair would change the world. “It changed our world,” he says, bitterly. The first person to testify in the film, a young Northerner, recalls how his former maths teacher, Mr McKilroy, remained silent when he encountered him in uniform after his first tour in Basra. He was hoping his former teacher would at least ask: “How are you?” or “What’s it like out there?” But nothing.

The testimonies are interspersed with black and white footage that offers poetic (sometimes bordering on kitsch) glimpses of the servicemen’s lives back in Britain. The relatives who got left behind (also played by actors) stare directly at the camera. Most of this film makes uncomfortable viewing. Often the testimonies tail off making you wonder what happened next. All this is very effective. However, the film’s slick, stylised look detracts somewhat from the gripping, often moving accounts. Why use actors and not real people? It also gets a bit repetitive.

The credits reveal that the testimonies are drawn from a long list of servicemen and women while the people in the film are simply referred to as man #1, man #2, woman #1, etc. Have the accounts been amalgamated from several sources? This is slightly disappointing and further reduces the authenticity. Even so, this film is worth watching for the valuable insights it gives into the lives of those who have gone out to Iraq to fight Blair’s war.

Jobson said in May when he started shooting the film: “Like many people I was angered by the Iraq war and like most people did nothing about it. This is my response to that apathy. In the film although it appears that the speakers are the ghostly presence, it is in fact we the audience who are the somnambulists, it is we who were sleep walking in the build up to the war and its tragic aftermath.”

The Somnambulists (UK, 96min) will be screened at the London Film Festival on Friday, 14 October, at 21:00, on Saturday, 15 October, at 15:30, and on Monday, 17 October, at 13:00. Go to the LFF website (http://www.bfi.org.uk/lff) for further details and to book.