The Colditz Story was one of a number of movies the British made during the Fifties which relived the victories and bravery of their armed services during WWII. Often these movies starred John Mills. The Colditz Story is based on fact. Colditz Castle in Germany was used to imprison the most incorrigible prisoners-of-war, those who persistently made escape attempts. British, French, Polish and Dutch officers were sent there. Unfortunately for the Germans, they wound up trying to keep inside men dedicated to escaping, and who had skills they now could share. The result was that more prisoners of war escaped from Colditz than from any other prisoner of war camp in either the First or Second World Wars.
The movie is based on the memoirs of Pat Reid (John Mills), who served as an escape officer at Colditz and then was one of the first to break out and make it back to England. While the movie is a bit dated, it also is a dramatic and efficient telling of escape attempts, ruses played against the German captors and, of course, of the unfailing courage and good spirits of the British officers. Take the film for what it is, a demonstration for British audiences of the pluck and courage of their military during a horrendously threatening war which they won, and you won't be disappointed.
If you're fond of old British movies, you'll recognize, among others, Eric Portman, Lionel Jeffries, Bryan Forbes and Ian Carmichael. The DVD I saw has a picture and audio in very good shape considering the age of the movie.