The characterization of Neville Sinclair was inspired by movie star Errol Flynn, or rather by the image of Flynn that had been popularized by Charles Higham's unauthorized and fabricated biography of the actor, in which he asserted that Flynn was, among other things, a Nazi spy. The film's Neville Sinclair is, like Higham's Flynn, a movie star known for his work in swashbuckler roles who is secretly a Nazi spy. Because Higham's biography of Flynn was not refuted until the late 1980s, the image of Flynn as a closet Nazi remained current all through the arduous process of writing and re-writing the script. The other real-life characterization was of Howard Hughes.