New question for you old sea dogs!
I'm now in July 1940 (Happy times) I requested Atlantic air Gap again (nothing else available yet) after successfully completing the spy mission the first time.
This time they sent me to: 'Intercept convoy and sink two ships' i got to the x on the map, and hung around for a day or so and only saw 2 Whales.
Then i had one of those convoy reports and went to try and intercept it, about 200-300km away i got a message from BDU saying 'cease all operations, continue on own initiative' that's when i noticed the above objective was in red (fission mailed

) and said complete, even though i didn't see squat or complete it.
I've seen a few posts on here about it, and i know that from TWoS FAQ it says they're not really necessary.....but i'm guessing, and have read, that there is some sort of invisible patrol zone there? Probably 100-200km?
I've got a save from when i arrived that i can reload.
Happy hunting,
John.