If it had ever been completed, Josef von Sternberg’s big-budget 1937 adaptation of Robert Graves’s I, Claudius for Alexander Korda might have been his masterpiece. But a series of calamities plagued the production, and all we have left today are some tantalizing rushes–and this excellent 1968 British documentary about the doomed project hosted by Dirk Bogarde, which includes many of these rushes and interviews with surviving participants, including Graves, Sternberg, Merle Oberon, and Emlyn Williams. But the best reason for seeing this film is the glimpse we get of Charles Laughton’s extraordinary performance as the crippled, stuttering, and otherwise afflicted Claudius. An actor who underwent torturous preparations for some of his roles, Laughton drove Sternberg and others crazy with his agonizing over getting this part right. But when he finally locked Claudius into place, he produced what is arguably the greatest piece of acting in all of sound cinema: better than Brando, better than Olivier, better even than Chaplin in Monsieur Verdoux. The evidence is there to be seen (and heard) in two stunning scenes–Claudius’s groveling at the feet of Caligula to save his own life, and, even better, his assuming power over the Roman senate–and the wonderful thing about this documentary is that it allows us to see him building and refining this monumental role step-by-step. (Film Center, Art Institute, Columbus Drive at Jackson, Thursday, November 12, 7:30, 443-3737)