After the German use of such vessels had been identified as a weakness that could be exploited to break the Enigma code, Lauenburg was captured and sunk on 28 June 1941.

[citation needed] The British cryptologist Harry Hinsley, then working at Bletchley Park, realised at the end of April 1941 that the German weather ships, usually isolated and unprotected trawlers, were using the same Enigma code books as were being used on U-boats.

Hinsley realised that if the code books could be captured from one of these trawlers, the naval Enigma system could be broken, with British intelligence able to decipher messages to U-boats and discover their locations.

The problem remained that if the navy were to attempt to capture one of the weatherships, the German crew would have time to destroy or throw their Enigma settings into the sea before they were boarded.

Minutes later, Tartar steamed alongside and a boarding party seized Lauenburg and a large amount of material was collected, then the Allied warships sank Lauenburg with gunfire; confirmation of the sinking was sent by radio, but the boarding was specifically not mentioned so that listening Germans would not suspect the recovery of Enigma materials.