The body was in a navy liferaft, arms outstretched over the sides, when it washed ashore on Christmas Island, a speck in the Indian Ocean 1,600 miles (2,575km) from Australia.

It appeared that the corpse had been drifting in the seas for weeks. The sailor’s overalls were shredded and bleached. He was buried in an unmarked grave on the island.

That was 65 years ago. “Who he was, we will never know,” wrote an islander in his journal.

The writer could not have foreseen the modern-day identification techniques that would become available to help Australian investigators to the verge of naming the lone sailor.

They have narrowed his identity to one of three of the 645 men who perished in Australia’s greatest and most mysterious naval disaster — the sinking of the 7,300-tonne battle-cruiser HMAS Sydney,the pride of the fleet, in November 1941. No trace of the wreck has been found and no bodies recovered — save for the Christmas Island corpse.

Two families were contacted by the Australian Defence Ministry last week and asked to provide DNA samples that the investigators hope will finally yield the name of the sailor. The relatives of the third — and last — possibility have not been traced.

Helen Blackburne, 84, was stunned when she was told that the sailor may be her brother. SubLieutenant Allen King was 26 when the Sydney went down after a battle with the German raider Kormoran. “I couldn’t believe it when they said they may have found him. We’ve never forgotten him,” Mrs Blackburne said.

There are 13 miles of documents in Canberra’s National Archives relating to the loss of the Sydney, which has confounded military historians for decades.

None could answer the most human of questions; who was the tall, young sailor in the raft? Last November an Australian navy team, after a six-year search, found his grave. The skeleton was preserved almost perfectly.

The remains were examined by pathologists at the University of Sydney. It was hoped that a dental examination may have helped the identification, but they learnt that only half of the Sydney’s dental records still existed. The rest had gone down with the ship. The surviving dental records did enable investigators to eliminate more than 300 crew.

An examination that identified the sailor’s approximate age and height when he died eliminated another 200 crew members. That left about 100 potential matches — still too many for a DNA-testing programme of relatives.

The investigators then turned their attention to the scraps that remained of the sailor’s clothes. They found that he had been wearing overalls — and was therefore an officer or warrant officer in engineering.

Commander Matt Blenkin, one of the investigators, said: “We established from bits of weave found with the press studs that his overalls were white, not blue. There were only three officers authorised to wear white overalls.”

Commander Blenkin now hopes that DNA extracted from the teeth of the skeleton will match that supplied by relatives. A result is expected within the next month.

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