At 16.55 hours on 14 Feb 1940, U-48 fired a G7e torpedo at the unescorted Sultan Star (Master William Henry Bevan) southwest of the Scilly Isles. The ship was struck on starboard side aft and sank by the stern with a heavy list after 20 minutes. One crewman was killed by the explosion. The survivors abandoned ship in the lifeboats, only the radio operator stayed in the wireless room until the last moment and was picked up by one of the boats after jumping overboard. He was later awarded the MBE and Lloyds War Medal for Bravery at Sea.

The attack on Sultan Star was witnessed on the horizon by the destroyers in the screen of HMS Exeter (68) (Capt F.S. Bell, CB, RN), returning to the UK from the Battle of the River Plate. HMS Whitshed (D 77) (Cdr E.R. Conder, RN) was immediately sent to assist and arrived at the scene about 40 minutes after the torpedo hit. The destroyer located the U-boat and her attack was soon joined by HMS Vesper (D 55) (LtCdr W.F.E. Hussey, DSC, RN) and HMS Acasta (H 09) (Cdr C.E. Glasfurd, RN). They claimed the sinking of the U-boat, which in fact escaped undamaged at dusk and reported that 22 depth charges had been dropped. The survivors were then picked up by HMS Whitshed (D 77), the half of them later transferred to HMS Vesper (D 55) and all landed at Plymouth the next day.