On 14 March 1942, Wanlyn departed on his 27th patrol in the Gulf of Taranto. On the night of the 18 March he sighted a submarine on the surface and determined her to be hostile. He engaged with a full spread of torpedoes, and the submarine blew apart and sank. The submarine was later identified as the "Tricheco" was lost with all hands. There was no counterattack, but motor torpedo boats shadowed her movements for hours which ran down her battery and oxygen. The following day Wanklyn moved to St Cataldo Point hoping to find a softer target for his deck gun. The lookouts sighted four vessels, a trawler and three fishing smacks. Wanklyn ordered the submarine to surface 100 yards from the trawler, "Maria". His officers gestured to the crew to abandon ship and "Upholder" fired seven shells into the vessel which sank. The Smacks fled close to shore. The action had lasted 14 minutes and Wanklyn decided it was too dangerous to give chase. On 23 March "Upholder", "Proteus" and "P36" loitered off Taranto in the hope of engaging Italian warships. One convoy was signed and Wanklyn fired on a light cruiser but misses. All three returned to Malta without success.