For almost 100 years the remains of Mudgee’s Corporal Athol Goodwin Kirkland lay in Crucifix Corner Cemetery, near Villers-Bretonneux in the Somme, under a headstone reading “unknown corporal of the 34th Battalion AIF”.

Now Prime Minister Tony Abbott has laid a wreath beneath a new headstone, with Corp Kirkland’s name in bold letters, above the epitaph “I once was lost but now am found”.

An amateur sleuth in Fremantle, Western Australia, who seems to have a knack for identifying nameless soldiers, decided the old headstone was a puzzle he could solve.

Last July Andrew Pittaway, an archivist at Fremantle Council, saw a photograph of the grave “and I thought out of interest I would check how many corporals at Villers-Bretonneux came from that battalion,” he told Fairfax Media.

“A couple of years ago I identified a soldier in a grave in Belgium, so I thought I would give this a try as well.”

There was only the one match. So Pittaway thought he should research where the man died, and that matched too. From the official records he found that a fellow soldier had said the corporal was buried in the same cemetery where they retrieved the body.

“It was all tying up,” he said. So he wrote to the Commonwealth War Graves office, and they agreed with his findings.

Athol Kirkland was a labourer from the Mudgee region, who enlisted in July 1916.

After training in England he joined the battle in France in April 1917, where he was gassed, went to hospital, returned to the fight, won several promotions then died in action in early April 1918 during the first battle of Villers-Bretonneux, defending the Western Front. His name is one of those on the Australian National Memorial, among 10,700 Australians who died in France in the World War I with no named grave.

The dedication ceremony on Sunday was attended by Athol Kirkland’s great, great niece Cheryl Maree Rowe, her husband Richard, their son Chad and his wife Jenny, and their baby son Finlay.

“Today we name and honour him,” said Monsignor Stuart Hall, the navy chaplain who blessed the headstone. “I felt really pleased that the family at last had some closure,” Mr Abbott said.

“Thanks to the diligence of our researchers we have the name and the grave … he that was lost is found.”

Cheryl Rowe said she felt very emotional during the service. “I thought it was wonderful and we are very very grateful for everyone putting all this together,” she said.

“It means a lot to my family. I’m a bit sad that I didn’t even know about this part of my family’s history. But it’s all brought together now.”

Chad said he felt proud to be part of a family that served in the war.

“It’s telling that we’re Athol’s closest family, he died so young that he was unable to have his own family,” he said.

Little 11-month-old Finlay had his photo taken with the prime minister and got a coin from the Chief of Defence. “I’m not sure he knows what it means yet. But in the future, yeah,” Chad said.