In January 1941, HM Trawler Lady Shirley underwent further conversions to enable its use in anti-submarine duties. After joining 31st Anti-Submarine Group at Gibraltar, Lady Shirley sank U-111 off the coast of Tenerife on 4th October 1941
Operating alongside trawlers Erin and Lady Hogarth, Lady Shirley’s Watch Officer observed the tower of a U-Boat. The Captain altered his course and launched an attack with depth charges. The U-Boat surfaced and as Lady Shirley manouevred to open fire, the German crew responded with a hail of shells. The U-Boat eventually went down and Lady Shirley lifted 45 survivors from the water. Later, Lady Shirley came under torpedo attack from U-374 off the coast of Gibraltar.
At around 0345hrs on 11th December 1941, the Captain of trawler St. Nectan observed Lady Shirley enter a rain squall that lasted for around 25 minutes. At 0410hrs, the trawler had vanished. There is no evidence to suggest a U-Boat sank the Royal Navy vessel.