Eighty per cent of Allied intelligence on the Nazis came from photo reconnaissance. Almost 36 million pictures were snapped mostly by Spitfire pilots in hazardous flying missions and examined by experts back in Britain.More importantly at the RAF Medmenham base, where the elite Photographic Reconnaissance Unit operated from, they took pictures in 3D by taking pictures with a 60% overlap then by viewing them through stereoscopic lenses.All of a sudden you could see the details of the trucks outside a factory and work out what it might be carrying or measure the heights of buildings.It took a certain type of person to analyse the data and also work in the dark and take a best guess. Xavier Atencio, a Disney animator was a resident expert as part of the US air force contingent.Operation Crossbow was launched to bomb the rocket sites as evidence emerged that the Nazis were planning to use V planes that were unmanned drones to bomb southern England.The documentary is made to look like an adventure with reconstructed scenes, interviews with veteran pilots, photo interpreters, military experts and computer modelling.It was an interesting take in a little known story of how the allies won the war.