So as not to hijack the other thread...
This is actually a Coastal Command film, however Bomber Command used the same thing at night to evade nightfighters. The corkscrew bit starts around 5:50.
http://www.youtube.com/watch?v=OzKmzXNq9m8Your opponent is the Hun. Is that clear?
The Hun. The jolly, jolly Hun.
Good show.