To exert pressure on German naval forces Wanklyn undertook a patrol on 14 July. On 18 July he arrived off the Dutch coast. North of Terschelling Island he sighted three anti-submarine trawlers in formation. After spending an hour closing on the vessels he launched a single torpedo at 07:37, from a range of 900 yards, on a 125 degree track angle to bring all the ships nearly in line with the torpedo and maximise a chance of a hit. He heard the torpedo through the hydrophones. Two minutes later there was an explosion and the German submarine chaser "UJ-126" sank. For the next thirty minutes eight depth charges were directed at the submarine, the nearest detonating 250 yards away, before the enemy gave up and retired eastward. A curt statement in his report marked the victory: "The behaviour of the crew was most satisfactory."