Venturer was the lead boat of the British V-class submarine, a development of the successful U class.

On completing trials and working-up, Venturer commenced operations patrolling the Norwegian coast for coastal traffic and U-boats leaving or entering base.

She also sank the German submarine U-771 on 11 November 1944 7 nautical miles (13 km) east of Andenes, Norway, off the Lofoten Islands.

U-864 was carrying a cargo of 65 tonnes of mercury as well as Junkers Jumo 004B jet engine parts (used in the Messerschmitt Me 262) to Japan,[2][3] a mission code-named Operation Caesar.

Launders had decided not to use ASDIC since it would betray his position and spotted the U-boat's periscope as her captain looked for his escort.

In an unusually long engagement for a submarine, and in a situation for which neither crew had been trained, Launders waited 45 minutes after first contact before going to action stations.

Exploding, U-864 split in two, and sank with all hands coming to rest more than 150 metres (490 ft) below the surface.