On 13 Feb 1941 the Cadillac (Master John Fraser Jefferson) left Halifax in station #91 of convoy HX-109, but the tanker was separated from the other ships when convoy was scattered by a strong gale with heavy snow showers during the night of 26/27 February. The next day, she met another straggler and the two ships were sighted by U-552 at 10.23 hours on 1 March. However, the U-boat could not get into a favourable attack position because they were forced to dive twice during the day to evade a Sunderland aircraft patrolling the area. HMS Malcolm (D 19) (Cdr C.D. Howard-Johnston, DSC, RN) was directed to the stragglers by the aircraft and led them to a group of three others ships from the scattered convoy. The five ships then continued in an ad hoc convoy proceeding in a line abreast formation with Cadillac as the outermost ship on the port side, escorted by the destroyer and HMS Mallow (K 81) (LtCdr W.B. Piggott, RNR).

At 23.56 hours on 1 March 1941 the Cadillac was struck on the port side amidships and further aft in the cross bunker by two G7e torpedoes from U-552 while steaming at 9 knots in fine weather about 150 miles north-northeast of Rockall. The tanker vibrated violently, took a list to starboard of 10-15° and the highly flammable cargo immediately caught fire, causing a massive explosion when the #8 tank blew up on the port side after about four minutes and illuminating all ships in the vicinity. With the ship settling by the bow and blazing furiously on the port side, the survivors tried to abandon ship on the starboard side. However, the small emergency lifeboat swamped during the launch as the forward fall was let go too quickly and its three occupants were thrown into the sea. The large rafts stored on the after deck proved to be far too cumbersome and heavy to launch them. 26 survivors managed to abandon ship in the starboard aft lifeboat, but it was surrounded by burning fuel and most men panicked as they could hardly breathe and see nothing except a wall of flame all around them. Some began calling for help, others were praying and then most jumped over the side and perished. Only five men stayed and took cover in about one feet of water at the bottom of the boat, which slowly drifted clear of the flames in the slight swell and the men frantically began to row away for about a mile with the only four oars left until they were completely exhausted. They then attracted the attention of HMS Malcolm by firing a rocket and were picked up at about 01.30 hours. The crew of the destroyer had seen a number of men swimming close to the flames but were unable to help them as they had lost their boats in the gale and stopping was too dangerous because the destroyer would have been an easy target being illuminated by the burning tanker. Unseen by the escorts, U-552 had remained on the surface nearby and Topp allowed his crew to come up to the bridge one at a time to have a look at the sea of flames before the U-boat subsequently left the area.

The Cadillac was last seen still blazing with a list to starboard and down by the head in 60°20N/12°18W at 05.30 hours on 2 March and apparently foundered later that day. The master, 31 crew members, two gunners (the ship was armed with one 4.7in, one 3in and two machine guns) and three passengers were lost. Five crew members survived, but four of them were badly burned and were landed at Stornoway in the morning of 3 March to be taken to a hospital as quickly as possible. However, the condition of one man was worse as he had no clothes on that could protect his skin and he died of his wounds the following night. The boatswain was brought to Londonderry to make a report and was then also taken to a hospital for treatment of his burns.