Night surface attack. Schepke never came under attack by the escorts. When he did finally attract attention from the destroyers he left the area, still on the surface.
Here is a view of that night from the other side.
http://www.convoyweb.org.uk/hx/index.html
Scroll down to HX.72.
And:
http://www.warsailors.com/convoys/hx72.html