In 1975, Rithy Panh was 13 and living in a suburb of Phnom Penh. His home was full of newspapers and literature. His sister worked at the National Museum. When he visited her at work, he pilfered the tamarinds from its gardens. He lit his father’s last cigarette before bed every night. It was an easy life.

Within the next few months, most of his family were dead.  After Khmer Rouge forces took the capital and plunged the country into turmoil, Panh was designated a hated “new person” because of his urban upbringing and sent to work in camps around the country, his old life utterly destroyed.

His father starved to death after asserting his right not to eat “anything that doesn’t resemble food fit for human beings”. His grief-stricken mother passed away on the deathbed of her 16-year-old daughter.

Panh lived. At the end of the war, he escaped to a Thai refugee camp, went to Paris and became a successful filmmaker.

In a new book, The Elimination, written with Christophe Bataille, he tells the story of how he survived the regime and, years later, confronted one of the men principally responsible for the atrocities: Duch, the commander of S-21 prison, where thousands were tortured and killed during the regime.

His memoir is an elegiac story of atrocity and grief recounted in succinct prose that, in parts, is as beautiful as it is devastating.

“And you, my sister, I never saw you again. I can still picture your colourful skirt when you would appear at the big, carved wooden door, and your bag filled with documents. I remember our walks together. Your words. And my caprices. I see you smile. You take my childish hand.”

His narrative, much like memory, the nature of which preoccupies him, is a liquid thing. There are no chapters. Passages recounting his experience under Khmer Rouge mingle with interviews with Duch, happening in the present tense, and his own musings. Other characters swim in and out of the prose – including the tragic Bophana, whose love letters sentenced her to death in S-21.

Panh writes with a cinematic eye, and his storytelling is best when in sharp focus, magnifying details even when they are horrific, which is often.

He casts an analytical eye on his own experience, elegantly marrying anecdotes with insights into the nature of evil. This image ends an account of a pregnant woman dying because Khmer Rouge leaders refused to send for the only doctor in town, a “new person”: “ . . . The young body, scarlet and deformed, was ideology itself.”

There are occasional slips. Emotion runs into rambling, and the combination of a lack of straightforward structure and esoteric references could alienate a reader unfamiliar with the Khmer Rouge story. His points of comparison – primarily the French and Chinese revolutions – are often neat, but risk intellectual showing-off.

For the most part, however, a tone of restrained, informed anger guides the prose.It is particularly evident in passages where he deals with Duch, his “subject”.

“I want to be able to touch my subject. I have no weapon, no bayonet, no fear, no desire. If I reach out my hand, I can touch the man.”

He speaks with utter certainty about whom and what has failed him and his fellow survivors in the years since the war.

The UN secretary who never replied to his letter, sent in 1979 after he moved to Paris as a teenager, detailing the horrors he underwent in his homeland. Sanctimonious Western critics who exonerated the regime.

As for the motivation of Duch and the other perpetrators, he refuses to fall victim to “facile” explanations.

“The banality of evil: a seductive formula that allows all kinds of misinterpretations. I’m leery of it.

“I don’t deny that some executioners and torturers can be ordinary people or that an ordinary person may become an executioner and torturer. But I believe in the uniqueness of the individual.”

For as much as this is a tremendous study of horror, and grief, it is the moments of goodness that are some of the most memorable. Not only sun-lit passages about the pre-Khmer Rouge years, but little acts of kindness during them, sweet interruptions amid tedium and suffering.

A portrait of his father becomes the emblem of what is simply “good”.

“In our democratic societies a man who believes in democracy seems to us an ordinary man. Maybe even a dull man. So I keep his yellowed picture in front of me in my Paris office. Let there be a banality of good, and let it be powerful. That will be his victory.” ​​​​​​​​

The Elimination by Rithy Panh and Christophe Bataille is published by  the Clerkenwell Press and for sale at Monument Books.