At 05.25 hours on 21 May 1941 the unescorted, unarmed and neutral Robin Moor (Master Edward W. Myers) was ordered to stop with a Morse lamp by U-69 about 750 miles west of Freetown. After questioning the chief mate that came aboard the U-boat, Metzler told him that he has to sink the ship in accordance with the prize rules and ordered the crew to leave their ship in 30 minutes. The nine officers, 29 crewmen and eight passengers (four men, three women and one child) abandoned ship in four lifeboats and the boat with the master then came alongside U-69. However, the cargo manifest shown to Metzler only confirmed his view that the ship was carrying contraband. The Germans gave four tins of bread, two tins of butter, some cognac and bandages to the lifeboats and then submerged. At 10.05 hours, the U-boat fired one G7e torpedo from the stern torpedo tube that hit Robin Moor on port side amidships, but surfaced again 40 minutes later because the ship only settled slowly and began shelling her with the deck gun, firing 39 rounds and causing the ship to sink by the stern after 17 minutes. The wooden crates carried as deck cargo floated free and were sunk with gunfire from the anti-aircraft guns.

The lifeboats initially remained together, but one of them became separated after three days. The occupants of three boats were picked up after sailing about 600 miles in 13 days by the City of Wellington and landed at Capetown on 18 June. The ten crew members and one passenger in the boat in charge of the third officer were rescued by Ozório on 9 June in position 00°46N/37°37W and two days later landed at Recife, Brazil.