Chugalug,
Hard to remember, but I seem to recall that one of Hitler's "turned " agents was made to pass back reports that the bomb had actually fallen in south London, not north as widely reported in the Press.
Aha ! thought German Intellingence - these crafty Englander, they want us to lower our sights a trifle, so as to move the aiming point south into open country. But we can see through that - we'll move it north and plant it in the city centre - so there !
With the result.........
(All hearsay). Danny.