– Professor Geoffrey Blainey, 1992

My family has been granted the rare honour and extraordinary privilege of having the life story of a relative read out at the Last Post service at the Australian War Memorial.

It's going to be an emotional journey for us on Saturday, May 14, when the crowd at the memorial – and those watching the webcast – hear about the sudden death of my mother's cousin, Pte Frederick John Lynagh of the 2/12th Field Ambulance.

Like the stories of all those who died for their country, this one makes you sad and, well, damn angry.

Jack, as he was known, died with several hundred other people when Australian Hospital Ship Centaur was torpedoed by a Japanese submarine at 4.10am on May 14, 1943, near Brisbane.

Could it have been an accident? Not bloody likely.

"It was night and the ship was so brilliantly lit that she must have seemed like a floating Luna Park," Blainey says. Spotlights were shining on the large crosses on the hull that denoted its mission, in accordance with Geneva Conventions.

However, the commander of submarine 1-777, Hajime Nakagawa, fired two torpedoes – one struck Centaur and it sank quickly, trapping many below decks. Of the 332 people on board, 268 died, including all but one of the 12 female nurses – and the three uncles of Canberra man Ted Leask.

I have written about Centaur previously so I was surprised to be moved when writing about the fate of a relative I never knew.

Frederick John Lynagh – Jack or Jacky to his family and friends – was born in Dalby in south-east Queensland on September 5, 1904. He joined an older sister in the growing family, and three more boys were born after Jack. Parents Larry and Jessie would later see all four sons go off to war.

Jack attended school at Bell, near Dalby, later becoming a provisional teacher at Bell State School in 1920. In 1931, he left teaching to work with his father and brothers, building houses and farm buildings in the local area.

The Second World War was barely three weeks' old when Jack presented for his Army medical and subsequently enlisted at Redbank near Brisbane. However, he was discharged on medical grounds in December 1939.

Not to be deterred, he tried again in August 1940 and was passed fit for service. He was attached to 6th Casualty Clearing Station as a nursing orderly and was posted to the small defence establishment of Fort Lytton at the mouth of the Brisbane River.

It was not enough for Jack. Finally, in September 1941, he was able to join the AIF. By December that year, he was with the Australian Army Medical Corps, attached to the 2/12th Field Ambulance, and on his way to Darwin.

He remained in Darwin until February 1943, surviving the carnage and confusion of the first bombings in February 1942 and all subsequent raids and serving with his ambulance unit during the civilian evacuation and the rebuilding of the town. His skills as a builder and carpenter were put to good use during this time.

Australian Hospital Ship Centaur, the myth of immunity, a 340-page book about the vessel's demise, uses strong prose to describe the wartime sinking of the vessel, in a chapter titled, "Three Minutes of Horror".

"The effects of a well-aimed submarine projectile brutally terminated the very existence of a non-combatant merchant ship, an unsuspecting victim with but a singular role of bringing succour and comfort to the casualties of war," the authors write.

"At 0410 AHS Centaur was a proud, fine and well-found vessel. Most of the 332 people on board slumbered peacefully in presumed safety.

"By 0413, three minutes later, she has disappeared off the face of the earth: gone, destroyed; a shattered, fiery hulk plunging downwards through an unforgiving sea to a grave a thousand fathoms deep. With her went most of those 332 lives, cruelly snuffed out.

"Many, mercifully, died instantly, without realising what had happened; many others did not, and many perished in unbelievably cruel and agonising circumstances. What made the Centaur sink in such a short space of time — not longer than the time needed to boil an egg?"

The authors supply the answer, saying the torpedo penetrated the main oil bunker tanks.

"A sheet of flame burst like a fireball in all directions, sky-rocketing high into the air and into the ship itself. The Centaur was doomed."

The bow of the vessel dipped, causing unsecured iron ballast to slide forward, increasing the list.

"The sea would not be denied," they say. "The human tragedy that accompanied those two to three brief minutes of horror is almost unimaginable.

"We know enough from contemporary interviews with survivors to take a guess at the unbridled terror and agony meted out to so many who never made it. Those who died instantly were the lucky ones."

I was stunned to read this extract from a survivor, describing the torpedo attack and subsequent explosion of the oil bunker:

"Pte Allan Pettiford woke to find himself on his feet, standing next to his lower bunk level. How he had got there mystified him. He woke to a ward in utter confusion but surprisingly little panic. His little pocket of bunks on the upper tween deck had somehow missed the worst of the blast, although when he tried to rouse his friend, Jack Lynagh, in the upper bunk, he failed. The shock wave must have killed him."

After decades of searching, the underwater grave of the vessel was discovered in December 2009. A national memorial was held in Brisbane in 2010, attended by then Prime Minister Kevin Rudd.

Jack's family members were among the congregation of about 600 people who attended the service to pay tribute to the victims of Centaur. Later, they were also among the 300 relatives who sailed on HMAS Manoora over the wreck site in September 2010 and placed about 100 wreaths on the ocean in memory of the victims.

For many years, the 2/3 AHS Centaur Association has been holding a commemorative event at the Australian War Memorial on May 14 each year, as well as in several other cities.

Last year, the memorial decided it could no longer support the stand-alone event and offered to dedicate the Last Post service on May 14 each year to the Centaur victims. This allows relatives, many of whom are elderly and cannot be in Canberra, to watch the event on a webcast.

At last year's Last Post service for Centaur victims, the life story of Army doctor Major Llondha Holland was told. He made several trips on the vessel to PNG to return wounded Diggers to Australia. At the time of the sinking, he was the senior physician on the vessel.

In January this year the memorial held its 1000th Last Post ceremony. Director Brendan Nelson had begun the event in April 2013 to personalise the roll of honour, which contains the names of more than 102,000 Australians killed in war and other operations.

The simple but sombre event regularly draws hundreds of people to the memorial at dusk, to hear the mournful note of the bugle, the swirl of bagpipes – and occasionally sobs as the story of a dead Australian is told.

My younger daughter and I placed a poppy next to Pte Frederick John Lynagh's name on the honour roll, after the Anzac Day dawn service eight years ago.

Now Jack's niece, Elizabeth Lynagh, will have the same opportunity to honour his memory, when she visits the memorial for the first time on Saturday.

"I never knew Uncle Jack – he was lost on Centaur some years before I was born," she said from Brisbane. "However, if he was anything like my father, he would have been a kind and gentle man, never one to push himself forward but always there for people when they needed him.

"My father and his two other brothers, Bill and Ray, known as Poss, were very private people, but I can't help but think that they would be quietly proud of the honouring of uncle Jack's sacrifice and memory.

"I have never previously had the opportunity to visit the War Memorial but have watched a number of Last Post ceremonies online. The ceremony is an amazing and enduring tribute to those on the roll of honour and I am very privileged to not only be able to attend one, but have a family member remembered."

A critical link between the reign of terror in Sydney and the tragedy of Centaur is revealed in historical files of the Army. The files show Japanese submarine I-177 took part in the attack on Sydney, shelling the city with her deck gun before submerging and heading north. It was waiting east of Moreton Island as Centaur steamed north.

"In accordance with the Hague Conventions, Centaur was clearly identifiable as a hospital ship, being painted white and marked with large red crosses," the history says. "She was fully lit and her voyage had been well publicised through neutral diplomatic channels, yet the precautions served only to make her an easier target when, at 4.10am on 14 May 1943, the Japanese submarine torpedoed the hospital ship. The ship exploded, probably as a result of a hit on the fuel bunkers."

Previously, Centaur had picked up German survivors from the Kormoran after it had been sunk by HMAS Sydney.

Centaur is a relatively well-known victim of Japanese submarines near the Australian coast but many other unarmed merchant marine vessels suffered the same fate.

One way to gain some perspective on the toll is to visit the walk of remembrance at Point Danger, on the Queensland–NSW border.

It was opened on May 14, 1993, conjointly with the Centaur memorial, perched high on this headland, with a stunning view of the Pacific Ocean.

The walk contains 41 plaques representing the vessels sunk by the wartime enemy in 1939-45.

The Tweed Heads Historical Society says few people are aware of the war at sea that raged along the Australian coastline, as Japanese submarines based in Guam prowled the eastern seaboard.

"This silent war was kept from the knowledge of the Australian public at the time to prevent panic and the loss of morale," writes Warren Keats in Walk of Remembrance.

"The Iron Crown, a BHP ore carrier, sank in one minute after being struck by a torpedo off the south coast of Gippsland, Victoria, taking 37 seamen to the bottom with her. The Wollongbar, a North Coast Steam Navigation vessel, sunk off Coffs Harbour, took the lives of 32 merchant seamen."

Lest we forget.

* Declaration: the writer is a member of the Centaur Association

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