The search for Australia's lost hospital ship
Gordon Rippon had just finished a four-hour watch on the bridge of the Centaur and was heading for bed.
It was 04:00 on 14 May 1943 and the Centaur, an Australian hospital ship, was just east of Brisbane.
It was heading for Papua New Guinea, where Australian troops were fighting the Japanese.
The vessel was carrying a full medical staff and the Cairns-bound 2/12 Field Ambulance unit, plus a merchant crew.
By 04:10 Gordon Rippon, the navigator, was in his bunk. Then came an "almighty crash" and he was blown across the cabin.
"I got up and looked out of the door... and saw a sight I will never forget," he wrote later to his father.
"The ship was way down by the head. All the forepart was one vast sheet of flames, and it was raining drops of burning oil."
The Centaur was sinking fast. He grabbed his life jacket and ran outside. "I just hopped over the side and swam away from the ship."
"The funny thing is that I never felt a bit frightened, only dazed, although I never thought for a moment I could get out of it. I just couldn't believe it."
Neither could Australia. The Centaur was marked as a hospital ship and protected under international conventions from attack. Yet it was torpedoed by a Japanese submarine.
Of the 332 personnel on board, 268 were killed, including 11 of the 12 nurses. The survivors clung to rafts or debris in the sea for more than 30 hours until rescue came.
The sinking caused outrage. Prime Minister John Curtin described it as a wanton and deliberate attack. "This deed will shock the conscience of the whole civilised world," he said.
Of the ship itself nothing was found. Survivors had drifted from the attack site and the Centaur's final resting place was unknown.
But more than 60 years later, things changed. It began on 17 March 2008, when a team led by UK-based maritime salvage expert David Mearns found the remains of another ship - the HMAS Sydney off Western Australia.
HMAS Sydney sank with no survivors in 1941 after a battle with a German raider, the Kormoran, which also sank. The death toll of 645 men made it Australia's worst naval disaster.
Finding the Sydney had been viewed as an impossible challenge because of the mystery over what had happened in the battle and the depth of the water.
But by piecing together information on its last-known location, including from Kormoran survivors, Mr Mearns defined a search area. Funding was secured for a high-tech on-water operation and first the Kormoran was located, followed a day later by HMAS Sydney.
As soon as the Sydney was found, Mr Mearns, said talk turned to finding the lost hospital ship.
"When I was still at sea… people were writing to me about the Centaur, saying this is a game-changer," he said. "A campaign started almost immediately on the other side of Australia: 'They found the Sydney, now let's go find the Centaur'."
One person who never imagined this was possible was Jan Thomas. Her father, Bernie Hindmarsh, was the doctor in Macksville, a small country town. When the war broke out he joined the army.
"He had three loves - that was medicine, the military and the sea," she said. He started on the Oranje, another hospital ship, but then moved to the Centaur, where he was one of four doctors on its medical staff. All of them died in the attack.
"Someone did see him in the water… and then they weren't seen again. He probably was sucked down when the ship went down."
As a child, Mrs Thomas chose to believe her father had swum to Brisbane, lost his memory, and that one day she would find him. "We grieved in isolation, like everyone else in those days," she said.
It wasn't until 50 years later that she met other families affected by the tragedy, something she found "particularly healing".
"I thought if we could have some way of organising ourselves … we could keep in touch," she said. That was the start of the Centaur Association.
Richard Jones, the association's president, lost an uncle, Gordon Jones, to the Centaur - but it could have been even worse.
His uncle was a doctor with the 2/12 Field Ambulance unit. His father, an army doctor also bound for Cairns, was offered a berth on the Centaur, but took the train.
"He got sea sick, he didn't think it was a risk they should take having two brothers together," said Mr Jones.
The discovery of HMAS Sydney, he said, galvanised the association since it was clear the technology existed to conduct a search.
"Our primary motive was to find, document and protect Centaur so that opportunists wouldn't go in and find the ship and desecrate it."
At the time, they were planning to raise the funds themselves. But the prime minister at the time, Queenslander Kevin Rudd, and Queensland State Premier Anna Bligh agreed to back a search. Together they came up with A$4m.
Narrowing the search
After a tender process, David Mearns was brought in. As before, he turned first to primary sources to fix the ship's last known position.
Two key contacts were Canadian Chris Milligan, a McGill University-based academic whose uncle died on the Centaur, and Capt John Foley, a Brisbane-based marine pilot and author.
In 1993 they published a book about the Centaur, based on years of research. Both met David Mearns to share what they knew.
"We went through each one of the personal files I had kept of the merchant crew members I had contacted - the survivors. We would go through what they said, what they remembered about the event, trying to get as much firsthand information as possible," said Prof Milligan.
Narrowing down the area was critical to achieving an effective - and affordable - search.
But there was a good deal of misinformation. Brisbane had, until 1943, been relatively untouched by the war, so the disaster made a huge impact. Some people believed, erroneously, they had heard the explosion or felt furniture shake from the blast.
For years many also believed the wreck of the SS Kyogle, a ship sunk by the air force in the 1950s for target practise, was the Centaur, and there were other false leads.
"There were some suggestions that the Centaur was about 20 miles north of where it is. Local fishermen were bringing up bits and pieces, they were getting their nets fouled on something," Capt Foley said.
"David had to contend with that… But I said: 'It's not there. It's where Gordon Rippon says it is."
About 40 minutes before the attack, the navigator had plotted the ship's position. And - despite questions over its accuracy - he was later very sure he had it right.
Two things worried Mr Mearns about Gordon Rippon's figures. If correct, then the survivors had drifted in the opposite direction to the prevailing current. There were also questions over whether he could have seen a lighthouse used in his calculations.
"We were using super-computers in terms of the oceanography to try to figure this out, that's how difficult it was," he said.
By December 2009, however, Mr Mearns had narrowed down an area and the operation could begin.
The search zone was a 1,365 sq/km box east of Moreton Island.
Inside the box, 15 "tracklines" formed a grid pattern. Over several days, side-scan sonar was towed along these lines, at the end of a 10,000m cable, to check the entire area.
"I was pretty confident, but I wasn't guaranteeing it to anyone… The two biggest concerns were environmental - the sea bed was very, very rugged and the currents were very strong," Mr Mearns said.
Inside the area, he wrote in his diary, there were three submarine canyons with walls rising 600m or more, making identifying a shipwreck even harder.
By day six the team had identified six targets worthy of closer inspection. Five turned out to be geological structures - which left one.
Closer examination was needed to obtain a higher-resolution image of the target, which then had to be correctly interpreted.
"What I knew was that on the basis of that sonar image alone I would have to say to [politicians] and most importantly to the families that I believe this is the Centaur," said Mr Mearns.
"I wanted to be absolutely sure. So I made them drag the sonar past the wreck until in my mind it was unmistakeable."
Hats and boots
It was the Centaur. On 20 December 2009, Australians were told that the nation's lost hospital ship had finally been found.
The ship lay, Mr Mearns wrote, on the lower flank of a narrow gulley at a depth of 2,059m.
It was, he wrote, less than one nautical mile from the position calculated by Gordon Rippon - "the best testament you could make to a man whose life was spent navigating the high seas".
The next step was to get a robot submersible down. On 10 January, the first images emerged.
Initially it looked like utter devastation, said Capt Foley, who was with the team, because the first pictures were in the exact area where the torpedo had struck.
More of the white hull and the anchor came into view, followed by the paravane, a long pole used to snare mines. Then they could see the green band and red crosses that marked the Centaur as a hospital ship - the crosses still red despite decades underwater.
The ship's bell was found wedged between two pipes on deck. It was lying with its name uppermost, said Capt Foley, "almost as if somebody's put it there thinking someone will want to see it one day".
There were other surprising finds. Several boots and two felt slouch hats - as worn by Australian soldiers - sat on the sea floor.
"No-one could believe it," said David Mearns. "That a felt hat that the merest current would push away would be down there 66 years later. That was pretty stunning."
For the relatives, said Richard Jones, the discovery meant a moment of "gratitude, one of relief and one of joy and sadness". "Everyone found some comfort in knowing where their relatives were," he said.
A plaque containing a roll of honour and relatives' messages was sent down to the wreck. Special permission to place it on the ship was obtained, after a test-run saw a metal plate sink into the surrounding sediment.
The wreck itself was protected under the historic shipwrecks act and the site marked as a military grave.
Finally, in September, a commemoration service was held at sea directly above the Centaur.
For Jan Thomas, who attended the service, finding the Centaur - and the way it was and continues to be marked by both families and the nation - brought a sense of peace.
"There is always a vacant place - but all these things are huge steps forward in the healing process," she said.
Mr Jones' father, then 98, was unable to take part. But finding the wreck meant a lot to him.
"I know my father was extremely grateful," he said. "In the family it was a very deep grief that was suppressed for so long."
"My father put a photograph of the plaque up on the book shelf at the nursing home… and it was always with him."
Who sank the Centaur?
Most historians agree the attack was carried out by submarine I-177 under the command of Capt Hajime Nakagawa.
He was jailed for six years in 1948 at the Yokohama Class B war crimes trials for machine-gunning survivors of three sinking British merchant ships.
But no case was brought over the Centaur. Nakagawa denied sinking the ship. Chris Milligan, who studied the investigation reports, said war crimes interrogators questioned him in depth and concluded he was lying, but did not have "enough information that would stick to him".
The motive for the attack remains unclear. Rumours circulated that the ship had been carrying munitions, but this is now understood to relate to the rifles carried by some ambulance drivers of the field ambulance unit to defend their patients, which was permitted.