From what I understand it had to recover practise torpedoes, not torpedoes shot in anger, and only in home waters.

Before the War HMS Elfin was a torpedo recovery vessel and a tender for the submarine fleet. The home port was Portland. During the War, the name was changed to HMS Nettle. It moved to Blyth, were it was used on the River Tyne to escort submarines (British ones I think) in and out of the harbour, so that submarines weren't attacked by British airplanes. From 1943 it moved to Rothesay. After the War it moved back to Portland again, to assist the submarine fleet again. In 1957 it was sold. It briefly became a movie star, as it appeared in the movie “The Key”, but after that the Elfin moved to Holland to become a tank cleaning vessel and since 1989 a museum ship. This page has text (in Dutch), but also some old pictures:

www.elfin.nl/elfin.htm

The Dutch page has the same info, but only in Dutch :-)