At 00.31 hours on 26 Sep, 1941, U-203 fired four torpedoes at the convoy HG-73 north of the Azores and saw one hit and heard three detonations after diving. Later Mützelburg saw lifeboats and sank a damaged vessel by a coup de grâce at 06.34 hours (probably the Cortes). He claimed two ships with 20.000 tons sunk and one other damaged. In fact, three ships were sunk: Varangberg, Avoceta and Cortes.

The Avoceta (Master Harold Martin) was the ship of the convoy commodore Rear-Admiral K.E.L. Creighton MVO RN. 43 crew members, four gunners and 76 passengers were lost. The master, the commodore, five naval staff members, 19 crew members, two gunners and 12 passengers were picked up by HMS Periwinkle (K 55) (LtCdr P.G. MacIver) and landed at Milford Haven.
Three crew members were picked up by the Cervantes, transferred to HMS Stork (U 81) (Cdr Frederic John Walker) and landed at Liverpool. The Cervantes was sunk by U-124 (Mohr) later that day.