Some years ago I knew a chap who had been involved in codebreaking in the western desert in the days before Ultra - just stick and string stuff. The Italians could be pretty careless. He said that occasionally they could break a signal and have the result laid reverently on the CinC's desk, to be followed by a further signal from the original recipient saying
''Your XYZ received corrupt. Please send again''
and thus they were able to claim that they were reading the enemy's signals faster than real time.