Colditz.S1E13.The Way Out

Colditz is a British television series co-produced by the BBC and Universal Studios and screened between 1972 and 1974.
The series deals with Allied prisoners of war imprisoned at the supposedly escape-proof Colditz Castle (Oflag IV-C) during World War II, and their many attempts to escape captivity, as well as the relationships formed between the various nationalities and their German captors.
Colditz was created by Brian Degas working with the producer Gerard Glaister, who went on to devise another successful BBC series dealing with the Second World War, Secret Army. Technical consultant for the series was Major Pat Reid, the real British Escape Officer at Colditz. One of the locations used in filming was Stirling Castle.
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Written by Bryan Forbes
The story of a Scottish commando named McDonald (Prentis Hancock) who receives a "Dear John" letter from his wife saying she is pregnant by another man.