In an interview made by former POW John Coast Boulle outlined the reasoning which led him to conceive the movie character of Lt. Col ' .
Former POW John Coast formed a part of the BBC2 documentary Return to the River Kwai in 1969 .
In an interview made by former POW John Coast , which formed a part of the BBC2 documentary Return to the River Kwai in 1969 , Boulle outlined the reasoning which led him to conceive the movie character of Lt. Col ' .