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interestingly Guy Gibson says they thought of themselves as pure fighters when returning from a bombing mission whilst flying a Hampden !
Couldn't have been too busy after June 1941. Luftwaffe intruders over Britain didn't amount to a hill of beans after Operation Barbarossa began.
Bombers taking off don't matter if they aren't hitting anything of importance and RAF Bomber Command wasn't during the first half of WWII. So Germany decided their light bombers could do more good on the Russian front. If RAF Bomber Command had been inflicting more damage the German decision might have been different.
From fall 1940 through May 1941 Germany conducted large scale night attacks on Port of London and Port of Liverpool. That sort of precludes the need for night intruder operations.