Sowerbutt's Adversary

Leopold Gerhard sat in the Captain’s cabin of U-boat 99 which had left Lorient in southern Brittany a couple of days earlier. He wore the uniform of a Leutnant zur See, but the crew had noticed that Kapitänleutnant Otto “Silent” Kretschmer listened to him carefully. 

http://www.amazon.com.au/Colour-Camouflage-Hitlers-Sowerbutt-Novels-ebook/dp/B00RQ62KFO