 While some people may think that this film was inspired by Franz von  Werras escape from a Canadian POW camp as portrayed in  _One That Got Away, The (1957)_ (qv). Von Werra wasnt sent to  Canada until Jan 41 and his escape wasnt reported until he got  back to Germany in April 41. This film was written as Powell &  Pressburger went to Canada in late 40 and production was under way  by Jan 41. Powell & Pressburger wouldnt have heard about von Werra  until the film was almost completed.