An estimated two million people, or one third of Cambodia’s population at the time, were “smashed”, to use Khmer Rouge terminology, in an orchestrated campaign of mass murder. Led by the infamous, enigmatic and reclusive Pol Pot, the Khmer Rouge carried out the merciless slaughter of their fellow countrymen, women and children during a four-year period between 1975-1979 in the name of a peasant revolution ideologically based on an anti-intellectual communism that returned the nation to Year Zero.

Incredibly, but not unbelievably, the outside world did not simply stand by to allow the sustained and systematic atrocity to occur, but at various times during the purge the governments of the United States, Britain, France, Thailand and China positively aided and abetted the Khmer Rouge. The US even helped fund the party’s revival so that, four years after the Khmer Rouge had been overwhelmed and driven into a no-man’s land on the Thai border by the Vietnamese military, it was very nearly returned to power.

Were this the stuff of a novel it would be not be credible. To this day the British government, then led by Margaret Thatcher, has never admitted that SAS troops trained the Khmer Rouge in guerrilla fighting, weapons technology and sabotage. The international community’s complicity in the Khmer Rouge massacres is documented meticulously by the author, providing the context for a rather more personal quest: to find the lost executioner Comrade Duch (pronounced Doik), pictured right, head of the secret police and commandant of Tuol Sleng, the prison in Phnom Penh where tens of thousands of innocent Cambodians were photographed before being tortured and summarily executed.

The photographs of the dead at Tuol Sleng – which is now a museum where the images are hung on a wall row upon row – is Dunlop’s starting point; finding and exposing Duch his grail. A photographer of note with a body of work behind him, Dunlop is motivated by a personal conviction to see justice upheld having spent many years living and working in Cambodia. His first encounter with the photographs of the deceased at Tuol Sleng propelled him in his quest that at time borders on obsession: “If ever we were to understand the Cambodian holocaust, and bring any measure of justice, finding Duch and others like him was vital.”

At all times, Dunlop is engaged, probing, questioning and diligent; he interviews countless survivors, murderers, including Prak Khan, who personally tortured and executed thousands at S-21 (another name for Tuol Sleng) – “I had the impression I was somehow speaking to an empty shell” – and several former Khmer Rouge, some who have recanted,  others who hold doggedly to their beliefs.

Occasionally, Dunlop allows himself to feel rather than intellectualise his experiences, but more often than not he appears to find the interviewer/historian’s chair a more comfortable one than the emoter’s. At times, the effect is to dampen the book’s vitality, rendering it a little one-paced, enlivened only by the odd personal intrusion. We understand the experience better when he allow us in to “feel” what he does. For example, he recalls photographing a gruesome scene and being unaffected at the time; only later on coming to edit the images does he feel nauseous. It is as if, understandably, he has become inured to feeling, a point he acknowledges himself when he admits, “Photography had become a safety net. The camera acted as a filter for what I was seeing.”

Surprisingly for a photographer first and writer second (although his prose is accomplished), there are few photographs published in the book, his own or pertinently those of the murdered at Tuol Sleng that first haunted and later inspired him. Dunlop explains why: “The display of the images [of the deceased] becomes a passive act of remembrance, rather than a call for justice.” Part of a broader debate, he admits, but it also appears to be tied up with an internal struggle the author is wrestling with about the validity of photography as a medium, and therefore, as a photographer, his own conscience in continuing to practise the art. Dunlop treads on more certain ground when he sticks to his quest.

Eventually, Dunlop, along with acclaimed journalist Nate Thayer, does track down Duch, who is using the alias Hang Pin, and is, incredibly, working for a US aid agency, ARC, and espousing a Christian belief to which he had converted. After some deliberation Duch confesses to his crimes in what Dunlop feels is a pre-rehearsed speech (he must have known in his heart that this day would one day dawn) before giving himself up to the authorities. Several years later, and to this day, Duch remains in prison awaiting a trial that increasingly looks unlikely to ever take place. Not one single person has been tried for the massacre of more than two million innocent people. Staggering. Chilling.

Gordon Miller