In reply to an earlier posting - there have been several articles on the filming of the Dams Raid. At the time it was said that the Bomb was in fact still on the Secret list so its size and shape had to be modified, this had the effect of making the films "Bomb" far more visable to the camera. There were only 3 airworthy Lancs available at the time hence why a lot of the formation shots are of 3. Most of the RAF base ground filming was carried at at RAF Hemswell just up the road from Scampton including the final scene where 'Gibson' walks away. Richard Todd who played Gibson learnt enough when doing the filming to taxi a Lanc around although I believe he came a cropper years later when trying to re-inact this fact with what is now Just Jane.
The original is a brilliant film and I fear the film worlds over use of things like CGI in a new version will never look as good as a real Lanc thundering over the countryside!