Years ago a special panel of Bundesmarine officers headed by Flotillenadmiral Otto Kretschmer evaluated all data from German sources and data from declassified Royal Navy.
The consensus was good odds that U-47 sank herself with a circular running torpedo. According to logbooks, position reports and individual memories of veterans who participated in that convoy action, U-47 was on the opposite side of the battlefield from HMS Wolverine, making it impossible for HMS Wolverine to have sunk U-47.
This panel concluded that U-47 was sunk by a circular run of her own torpedo and not by HMS Wolverine doing at this time? Prien sank dozens of Allied ships and was great for the Allies that he was killed early in the war.