SC 26 comprised 23 ships and was escorted only by the Armed Merchant Cruiser (AMC) Worcestershire (Cdr J Cresswell).

SC 26 was opposed by a patrol line of nine U-boats, positioned at the limit of endurance to intercept east-bound convoys before the Western Approaches escort had joined.

On 1 April 1941 an outbound U-boat, U-76 (Hippel), on her way to join the newly formed patrol line south of Iceland sighted a west-bound convoy in the North-West Approaches.

As they did so, one of the boats on the patrol line, U-74 (Kentrat), made contact with an east-bound convoy, SC 26, which BdU determined to attack.

After sending a sighting report, Kentrat commenced shadowing, and was joined throughout the day by three other U-boats that were nearby.

The first assault, during the night of 2/3 April, was made by U-46 (Endrass) just after midnight; She fired on British Reliance, which sank; Alderpool, which was damaged, to be sunk later by the newly arrived U-73; and Thirlby, which had stopped to pick up survivors, but escaped harm.

As the convoy started to scatter, a 6th ship, the tanker British Viscount, was hit by U-73 and burst into flames, illuminating the scene.

Tennessee, carrying survivors from British Reliance, put into port in Ireland, while Tenax and Ethel R docked in Britain.

The U-boat arm had scored another victory, and by managing to shift its point of interception further west, beyond the range of the anti-submarine escorts, ensured a series of successes until Western Approaches Command could adjust.

Arbutus had been unable to capture U-76 and her prized Enigma machine, but this breakthrough was just 4 weeks away with the seizure of U-110 in May, with a profound effect on the course of the Atlantic campaign.