A bereaved mother shows the tattoos on her back that memorialise her son. Another has a shrine in her garden. The centrepiece is a single ceramic boot, because, she explains, her son had only one leg attached when he died. Her house is filled with objects bearing his image. She used to have a mug on which his picture appeared when it was filled with tea, but she could not bear to see him fade away when it cooled and removed it. Another produces a hand-written letter of condolence from Tony Blair. There is a smudge at the bottom, and she wonders if the former Prime Minister shed a tear as he wrote.

However sentimental, this grief is raw and intense. It is recorded by Morgan Matthews in The Fallen, which runs for three hours tonight on BBC Two. Every one of the 298 who have died while serving with the Armed Forces in Afghanistan and Iraq, up to the edit, is listed on an individual caption. Dozens are recalled by families, girlfriends and comrades. Family memories are interspersed with clips of the soldiers’ experience of war, from helmet-cams, mobile phones, webcams and reporters’ archives.

It is a hugely ambitious project and a leap of faith for Matthews, who has built a name for exploring quirky passions such as taxidermy and competitive pigeon-racing or delving into the lives of eccentric individuals (Blue Suede Jew, for example, followed an Israeli Elvis impersonator who believed his music could reconcile Israelis and Palestinians). What made him want to make this film?

“A year ago I saw a report about the latest British soldier to be killed,” he says. “It rated a small paragraph and a thumbnail photo on page four or five of the paper. I felt the public, myself included, were becoming disconnected from these deaths, desensitised even. They were being reported as just another soldier’s death, not taking on board what that loss meant. I wanted to know more about the people behind those photos and their families. The principle was to mention every single British service person who has died in the fighting.”

It was the BBC that told him he might need up to three hours. When I talk to him during the final edit he is struggling to get it down to length and has just asked for an extra five minutes. Is he worried about losing viewers? “It is quite hard to watch in one sitting,” he reflects. “It’s a brave thing for the BBC to do. But I like long documentaries. I was inspired to think it could work by When the Levees Broke, Spike Lee’s four-hour film about Hurricane Katrina, which made me realise the magnitude of that disaster. It was partly to do with trying to have that kind of impact.”

Contact was initially made via the regiments, which forwarded letters explaining the project to the next of kin of all the soldiers. “We spoke to over 200 family members, some just offering support, wanting to chat or send photos, even if they didn’t want to be filmed.” He had little idea of the end result. “I like to get out there with my camera and just start filming. It’s dangerous to have preconceived ideas.”

He refuses to be drawn on his own views on these conflicts. “I don’t think my opinions would be valid in this process. A lot of families do have issues with the Government about the motivation for going to war, but many don’t. Many have discovered that the media are only interested if there is a controversial element like lack of equipment.

“In the end, this is a film about grief,” he says, “about the way people deal with premature death, about the human cost of the war, and the way culturally, we deal with grief.”

The film shows an extraordinary range of ways of coping – or in some cases hardly coping – with loss as we move chronologically through the conflicts. A stiff-upper-lipped retired major finally cracks when he recalls the funeral of his officer son who took three weeks to die in an Edinburgh hospital. Another father has become an implacable antiwar campaigner. Others families are split asunder by their differing reactions.

Some of the amateur footage is staggering. We follow one young man’s last moments from an ambush in a Helmand orchard to the Chinook pilot’s film of the desperate attempts to save him on the rescue flight. Some of it is very hard to take. One soldier describes in horrific detail what happened when his comrade was blown up by an IED (improvised explosive device). A teenage girl struggles to come to terms with the desertion implied by her soldier father’s suicide, but Matthews insists that all the participants were keen to talk and free to tell him if they did not want particular parts broadcast.

Matthews accepts that Afghan, Iraqi and American casualties are far higher than ours, but that is not the point. “This is about the domestic situation over here,” he says. In the process he has produced an extraordinarily moving piece, which tells us more about our Armed Forces than a thousand news reports and more about British families than a thousand reality shows.

The Fallen, tonight, BBC Two, 9.05pm

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