Silver found in wreck of ship sunk by U-boat in 1941

The largest consignment of precious metal found in the sea – 200 tonnes of silver worth £148m – has been discovered in the wreck of a British cargo ship sunk by a German U-boat during the Second World War .

Odyssey Marine Exploration, an American underwater archaeology and salvage firm, will announce the discovery today with its plans to recover the bullion.

The SS Gairsoppa, an ageing steamer belonging to the British India Steam Navigation Company, was ordered into the Merchant Navy fleet at the outbreak of war. It was sunk by a torpedo in February 1941, after hitting heavy weather in the Atlantic and trying to reach safety in the Irish Republic.

Some of the 85-strong crew are thought to have made it to lifeboats as they came under machine-gun fire from the submarine. But after drifting for 13 days and for more than 300 miles only one sailor – Second Officer Richard Ayres – reached the Cornish coast alive.

The well-preserved wreck of the 412ft steel-hulled ship was found by Odyssey this summer, nearly 4,700 metres below the surface. The vessel had settled on the seabed in a fully upright position, with the cargo holds open and the bullion accessible via the hatches, using remote-controlled robotic submarines.

The Gairsoppa was carrying about 200 tonnes of silver to help to fund the war effort, sailing from Calcutta to Liverpool, via Freetown in Sierra Leone – an important staging point.

Under a contract with the Department of Transport, Odyssey will be permitted to retain 80 per cent of the value of the silver in return for taking on the commercial risk and expense of locating the Gairsoppa. If it brings all the bullion to the surface next summer, it will make about £118m.

Andrew Craig, the senior project manager, said: "We've accomplished the first phase – the location and identification of the target shipwreck – and now we're hard at work planning for the recovery phase."