Fortunately the BBC's promise to re-screen the film has been made good today. Whether the timing is good or bad is perhaps debatable, given the current focus on prison regimes in Iraq, but the film is, essentially, the "plucky comic relief" aspect of the subject.
Synopsis: Between the years 1939 and 1945, the English Public School went on a Grand Tour of Europe, and a few jolly chums who had got themselves lost once or twice were presented with exclusive accommodation in Schloss Colditz, courtesy of the Germans. There were many japes, and they got along well with their fellow guests (except for the French, who were determined to liberate themselves). Popular activities included digging, climbing, abseiling, dressing up, and generally baiting Jerry for his poor sense of humour. One or two chaps felt the need to stretch their legs further afield from time to time, but were mostly returned to the camp safe and well.
John Mills provides the lead as Pat Reid (on whose book the film is based), and the only things missing from the film are some of the more entertaining escape attempts (such as dressing in drag or by attempting to seed the castle with dry rot).