Colditz Castle, one of the most notorious prisoner of war camps in Nazi Germany, was supposed to be escape-proof. But in the dark days at the end of World War II, a group of British officers dreamt up the most audacious escape plan in history.
In a secret workshop in an attic in the castle they constructed a two-man glider out of bed sheets and floorboards. They were going to fly to freedom from the roof of the castle, but the war ended before they could put their plan into action, so no one knows if it would have worked.
Now the Brits are back to finish the job. Cambridge engineer Dr Hugh Hunt leads a crack team of aeronautics engineers and carpenters to rebuild the glider in the same attic using the same materials.
Then he attempts to do something the prisoners never got a chance to try: use a bathtub full of concrete to catapult the glider off the roof of the castle.
It's also a personal journey for Dr Hunt: his uncle, Major Will Anderson, was a prisoner in Colditz, as well as an arch-forger.
Hugh goes behind the legend, and finds out what it was really like for the men imprisoned here, and the families waiting for them back home. Along the way, archeologists open up some of the castle's other famous escape routes.
Then, after a 70-year wait, the team finally find out if the legendary glider escape would have worked.