premise: True as a Turtle is a 1957 British comedy film directed by Wendy Toye and starring John Gregson, Cecil Parker, June Thorburn and Keith Michell. In the film, a young couple embark on a voyage on a ketch named "Turtle". John Coates wrote the screenplay, based on his novel of the same name.
hypothesis: True as a Turtle had Jim Smith in it. 
reason: It said what the stars were but there are always many extras. It might have had someone named Jim Smith in it in a small roll, there's no way to know. 