Pier Paolo Pasolini's Salò or the 120 Days of Sodom was released in 1975 and became an instant milestone in the cinema of transgression. A political fable, it tells the story of four men who in the waning days of Fascist Italy retire to a villa to enjoy their perversions and sadism at the expense of the young people they have captured. Torture, rape, murder and degradation are explicitly depicted in a way that remains shocking to this day. I talk with Jason Wood, author and film programmer for the BFI, about this electrifying, challenging film.