From extra reading it seems that the British were very successful both with Espionage and gaining German intelligence however it seems that most if not all German spies were subject to the double cross system. Therefore is it fair to argue that Britain essentially "won" this section of the war from the outset and what influence did this have on the war?
piggybacking: has anyone written on just WHY British intelligence was so much better than German? I asked the question before but got no response:
The Wikipedia article on m15 says that they caught all but one of the ~115 German spies sent into England, converting many to double agents. Another thread from this month mentions how German intelligence failings regarding RAF numbers was a significant factor in the RAF overcoming the Luftwaffe. What was it that made M15 so damn good? Or Germany's intelligence so damn bad? The Wikipedia mentions that many German spies turned themselves in - was there a moral qualm involved?