On 9 April 1940, HMS THISTLE (Lt Cdr W F Haselfoot) was ordered to dive off Stavanger at her discretion and attack ships reported there. She signalled back her intention to comply with the orders on 10 April, reporting that she had 2 warheads remaining. She also reported an unsuccessful attack on a U-boat off Skudesnes.

In response to this, her orders were changed, and she was directed to patrol off Skudesnes, in the hope of another opportunity to attack the U Boat. German records reveal that, in the event, The U Boat detected THISTLE on the night of 10 April and attacked her successfully. There were no survivors. The official date of 14 April 1940 shown in the listing below is based on when the submarine failed to return from patrol and was reported missing.

The U Boat was U4 which survived the entire war, surrendering in 1945.

In 2023, a Norwegian research vessel discovered a submarine wreck off Stavanger, Rogaland, Norway, which was thought to be that 0f HMS THISTLE and this has now (October 2023) been confirmed by the Royal Navy.  See this article and this article.