At about 18.30 hours on 4 September 1940 the unescorted and neutral Luimneach (Master Eric Septimus Jones) was stopped by U-46 with two shots across her bow about 170 miles west-southwest of Ushant and was sunk at 20.00 hours by gunfire after the crew had abandoned ship. The U-boat was returning from patrol and had no torpedoes left when the ship was spotted. Endrass was not sure about the nationality of the vessel and the survivors thought that the U-boat had been Italian. After being stopped, the men abandoned ship in one overcrowded lifeboat without provisions. Endrass ordered them to row back to the ship to launch the second boat and handed over rations, cigarettes and rum.

The master and eight crew members in the starboard boat were picked up by the French fishing boat St. Pierre, which transferred them to a Spanish trawler and they were landed at Pasajes, Spain on 13 September. The remaining nine crew members in the port boat were rescued by another French fishing boat and landed in France, where they were interned by the Vichy French authorities. While one Belgian and five Irish crew members were soon released and allowed to return home, the remaining three crew members (two British and one Maltese) were handed over as prisoners to the Germans.