Louisa Buck probes the many mysteries surrounding the amazing triptych painted by Hieronymus Bosch 500 years ago. Was his unique vision of heaven and hell the work of an orthodox Christian, or a heretic advocating salvation through sex? Was Bosch the first surrealist, or is this painting the product of a sick mind? The work has inspired modern artists, a ballet, a steamy novel, numerous LP covers and centuries of learned debate. Producer Mick Webb