OPENS JANUARY 23, CERT 12, 101 MINS During the Pol Pot-inspired genocide in Cambodia that killed an estimated two million people, S21 was a detention centre in Phnom Penh where 17,000 people were questioned, tortured and executed. Director Rithy Panh's documentary (showing until February 1 at the NFT) brings two of the three surviving inmates face to face with their former captors. We hear how the guards, many of them barely out of their teens, tortured and murdered prisoners. The guards claim they were brainwashed and indoctrinated. Still, it's apparent that in some dark corner of their souls they'd far rather leave untouched, they relished their duties. What's even more bizarre?at least to Western eyes?is that the killers and their victims now live side by side. There have been no Nuremberg-style trials. As the guards wander round S21 and talk about their duties as if they're reminiscing about some humdrum municipal job, Hannah Arendt's famous remark about "the banality of evil" seems more pertinent than ever.