On the afternoon of 21 October 1942, about north-north-east of Cape Ortegal (), "Graph" dived to evade a German Focke-Wulf Fw 200 long-range patrol aircraft. A loud hydrophone contact made Marriott believe a nearby submarine had likewise dived and, 12 minutes later, he observed its conning-tower against the setting sun. After pursuing the German boat, "Graph" fired four torpedoes. Explosions were heard, and also banging noises, leading the British to believe they had hit the other submarine and the banging noises were caused by her breaking up as she sank. In early 1943, Marriott was awarded the Distinguished Service Order for "great courage, skill and determination in a successful submarine patrol".