Great Escape: Secret film documents WWII prison camp breakout
31 July 2013 Last updated at 09:26 BST
A remarkable film showing life inside an Austrian prisoner of war camp - and a daring escape from it - has been obtained by BBC News.
It was made by French prisoners during World War II, with a camera smuggled into the camp among sausages.
Christian Fraser looks at the risks taken by the officers in the production of the film, as well as the escape bid, and meets the last remaining survivor of the team.