 Donald Pleasence (qv) had actually been a World War II prisoner of  war. When he kindly offered advice to the films director  John Sturges (qv), he was politely asked to keep his "opinions" to  himself. Later, when another star from the film informed John  Sturges that Pleasence had actually been a RAF Officer in a World  War II German POW Stalag camp, Sturges requested his technical  advice and input on historical accuracy from that point forward.