There are films I long to see and know I never will: Michael Powell’s Prospero; Orson Welles’ Heart of Darkness; Martin Scorsese’s Gershwin; Max Opühl’s The Duchess of Langeais.  Film history is haunted by the spectres of unmade movies, films which for whatever reason—cast reshuffles, vagaries of financing—never saw the light of a projection booth. […]