An incredibly brave and cunning group of French prisoners of war were able to construct a camera inside the Nazi prison camp they were being held at and film their conditions.

Their rarely seen footage is called Sous Le Manteau (Clandestinely). So professional is it that on first viewing you would be forgiven for thinking it is a post-war reconstruction.

Prisoners filmed the camp secretly with a camera inside a hollowed-out dictionary. It is in fact a 30-minute documentary, shot in secret by the prisoners themselves. Risking death, they recorded it on a secret camera built from parts that were smuggled into the camp in sausages.

The prisoners had discovered that German soldiers would only check food sent in by cutting it down the middle. The parts were hidden in the ends.

The camera they built was concealed in a hollowed-out dictionary from the camp library. The spine of the book opened like a shutter. The 8mm reels on which the film was stored were then nailed into the heels of their makeshift shoes.

It gives an incredible insight into living conditions within the camp. The scant food they were given, the searches conducted without warning by the German soldiers. They filmed it all, even the searches, right under the noses of their guards.