At the end of the nineteenth century, audiences were enthralled by the flickering image of an oncoming train in a Lumiere Brothers' short film; more than a hundred years later the immersive fantasy of Avatar enveloped audiences around the globe. Film is a communal dream, in which our fears and fantasies are revealed, often to startling effect. It has influenced our behaviour in small but significant ways, from the widespread abandonment of vests after Clark Gable's example in "It Happened One Night" to gangsters holding their weapons at movie-cool angles, improving their image but not their aim. It has intertwined with politics, helping to forge national identity, galvanise against a wartime enemy or warn of social upheaval via horror or science fiction. It has burrowed deep into our psyche, changing perceptions of history and memory - one study showed soldiers' recall may sometimes owe more to war films than actual experience. It has even raised romantic expectations that for us, too,