September Cruise of Kapitanleutnant Prien
After six weeks in Germany, Prien carried out a cruise lasting approximately 28 days:
He started operations by sinking the Belgian Ville de Mons on the 2nd of the month, N.E. of Rockall. Proceeding westward he sank the British Titan on the 4th when N.W. of Rockall, and it is thought that he then fell in with convoy S.C.2, … sinking on the 7th the Norwegian Gro and two British ships, the Jose de Larrinaga and the Neptunian. Following the convoy south-eastwards towards Ireland until after dark on the 8th, he sank two more British vessels, the Poseidon and the Mardinian, about 100 miles N.W. of Malin Head.
If this cruise has been correctly estimated as set out above the total tonnage sunk was 37,441. Prien claimed 46,250. It is perhaps relevant to recall that he has so far managed to out-distance any competitors’ claims.
October 1940 Naval Intelligence Bulletin