When I saw this was an Italian film about German Nazi spies in Britain 1940, I feared the worst.
However, despite some dodgy dubbing, it is all in wonderful technicolour, with some decent action scenes and explosions, and a plot which makes sense though it is fiction - all based on spies trying to sabotage RADAR during after after the 1940 Battle of Britain.
Real footage of WWII is intercut Ed-Wood-Style with newer flying scenes - some obviously filmed in a studio and some featuring model planes crashing into the see. Some showroom dummies are also blown up! Italian special effects but not bad for 1969.
I enjoyed it. The context of the Battle of Britain and the Blitz work, though maybe the 2 main characters look too alike and some 'British' and 'German' soldiers look rather too Italian...
So 4 stars.