As I understand it the Germans were great advocates of magnetic mines so assumed that everyone else (eventually) would be so devised zimmerit as a defence. An example of the fundamental weakness of Fascist logic.
Just checking up , thanks to Jim who pointed me in the right direction, and to your good self sending me here.
Reading about the " real " stuff I will NOT heating it up with a blow lamp. With this heatwave fires at Race Towers have been banned by management.
Hot House John