Wanklyn was called into action again on 15 May 1941. "Unique" had reported five cruisers and smaller craft convoying in the Straits of Messina. Simpson considered "Upholders" presence beneficial. Wanklyn set course for the convoy route to Benghazi and then towards Messina to maximise his chance of catching an enemy ship. Bad luck plagued the early part of the mission. A torpedo leaked and had to be reloaded submerged. A convoy was sighted but was too close to shore and could not be brought within range. "Upholders" Asdic had been knocked out. A faulty washer let in sea water which destroyed the insulation around an electrical cable. A signal arrived in the afternoon informing him of a convoy near Patras. Wanklyn's look outs spotted it—a tramp steamer, two tankers and a corvette, barely visible against the backdrop of the coastline. Wanklyn fired three torpedoes at 7,000 yards. One explosion was heard. Minutes later two more were heard but Wanklyn assumed they had struck shore. A 4,000-ton tanker was claimed damaged. Six depth charges were dropped but missed, roughly by one mile. On 22 May an Italian hospital ship was allowed to pass by without an attack.