OK this is a real long shot because I saw it when I was a kid and remember almost nothing about it.
It is in black and white, about WW2 and I am about 65% sure it is British.
The only thing I remember about it is that it involves a Nazi plot to take over the world with agents in the US,Brazil etc though IIRC the story itself is set in Europe.
I am not 100% sure but I think the last scene involves a man just walking into the distance.
I remember liking this movie when I saw it and I would really like to see it again.
I know there are some really knowledgable film buffs here who might be able to figure out what I am talking about. Or at least suggest the names of some films with similar themes.