The result is the most fascinating documentary about a failed movie since 1965’s “The Epic That Never Was,” about the abortive Korda-produced, von Sternberg-directed, and Charles Laughton-starring film of Robert Graves’ great novel I, Claudius.

(The director’s gift for comedy was manifested pretty spectacularly in his 1972 picture “ The Ruling Class,” with Peter O’Toole as an aristocrat who believes he’s Christ.) To exorcise his agony, he has made a documentary starring himself and featuring, in new interviews, other still-living directors who survived the Sellers Treatment, and even some figures who were Medak’s enemies during the cursed production of “Noonday Sun.” The experience still scars Medak, who considered Sellers a pal when they first resolved to work together.