Pictures: Aurora Trust Foundation and Imperial War Museum

THIS is the unmistakeable silhouette of a submarine, sitting upright, seemingly undamaged, on the bed of the Mediterranean.

This is Her Majesty’s Ship Olympus, found by marine archaeologists just three and a half miles off Malta, 70 years after she sank at the height of the struggle for the island.

Olympus fell victim to a mine dropped by the German Air Force as the Luftwaffe tried to pummel Malta into submission in the spring and summer of 1942.

Her loss ranks among the very worst disasters in the history of the Silent Service – of the 98 (or possibly 100) souls aboard, only 11 survived.

Although divers believed they had found the wreck of the 283ft-long boat back in 2008, only now with the aid of deep-sea technology has Olympus been formally identified by the Aurora Trust Foundation which worked with officials in Malta to locate the sunken boat.

Explorer Craig Mullen says the submarine sits upright “almost as though it was still operational – and ready to resume its voyage”.

Olympus' encrusted deck gun

He and his colleagues used robot submarines to record images of Olympus – she  lies at a depth beyond the reach of recreational divers – and which were used to confirm the wreck’s identity.

“The mine damage is clearly visible,” said Aurora’s director of marine archaeology Dr Timmy Gambin, who led the search for Olympus.

“Although covered in sea growth and home to numerous sea life, the wreck is in a surprisingly good condition – its distinctive features are clearly visible. The deck gun is slightly elevated and ready for action, and the bow and stern torpedo tubes are clearly identifiable.”

HMS Olympus in Grand Harbour, Malta, just before Christmas 1941. IWM A 6928

Olympus was built in the late 1920s for service in the Pacific and spent nearly a decade serving on the China Station. When the Italians declared war in 1940, she was dispatched west.

Although she was initially used on typical submarine patrols, by 1942 she was one of three boats which had been converted into underwater transporters – ferrying around 200 tons of supplies between Gibraltar and Malta on each run to help ease the Axis blockade of the island.

She set out on one such run on May 8 1942, carrying not just her normal complement of 55 crew, but more than 40 ‘passengers’ – crew from three sunken Royal Navy submarines, P36, P39 and Pandora – who were being sent back to the UK to help crew new boats.

About an hour out of Grand Harbour, and still on the surface, Olympus was shaken by a terrible explosion. Although crew thought at first that she’d been bombed, the submarine had actually struck an aerial mine laid by German aircraft. On this occasion, no minesweeper had been sent to clear a path ahead.

The crew were soon ankle-deep in water, the electric lighting became intermittent, seawater got into Olympus’ batteries causing chlorine to spread through the boat.

Despite the chaos – it’s unlikely there was a formal order to abandon ship – and the vast number of souls aboard, many men did get ‘top side’.

On the casing, officers urged men not to remove their submariner’s sweaters – they would provide good insulation in the water – but they did tell them to remove shoes and boots to help swimming.

“The  men removed them – and lined them up neatly on the casing as they went into the water,” said George Malcolmson, archivist at the Royal Navy Submarine Museum, who interviewed some of the Olympus survivors.

“They then set out as a group to swim towards Malta and, as daylight came, they watched the bombers come over and attack as they did every day at breakfast time.”

Some accounts say 11 men reached shore, others nine. It took the few survivors around five hours to get to land. Once eventually back in Britain, each one was personally interviewed by Max Horton, the WW1 submarine ace and leader of the struggle against the U-boats in WW2.

“In terms of numbers, the loss of Olympus ranks among the very worst of Royal Navy submarine disasters – right up there with the Thetis,” said Mr Malcolmson.

“The loss of the boat herself was of less concern than the loss of experienced submarines. Boats you can replace, but not the men.”