Could Ivan Milat have buried missing girls Kay Docherty and Toni Cavanagh in Primbee sand dunes?

A stark network of paths and roadway used to shore up this slice of land, but time has worn those surfaces away to rubble and the vegetation has ballooned upward and outward, blurring what were once well-defined ways in and out.

So worn are the paths that the ground turns soft in parts. Prod it with a stick and it falls easily, silently away, the truth of the place revealed: it's all sand dune out here.

"No one would hear you digging in this," says Dakers, nudging the ground with the toe of his shoe.

"You could drive over the top and park here, no one would see you.

"It's an easy dig."

The dunes have become an obsession for Dakers, a retired pastor best known in the Illawarra as the long-serving head of a not-for-profit that provided cheap groceries to the needy - the Hope Centre's now closed Illawarra Food Hub.

But before he was a pastor, Dakers was a cop. Constable Dakers was on the job in 1979 when the first reports came in of two missing girls, Kay Docherty and Toni Cavanagh. He remembers Kay's dad visiting Warilla Police Station in the weeks and months and years that followed - "have you found my daughter yet?".

Kay and fellow Lake Illawarra High School student Toni vanished from near a bus stop outside Warilla Grove shopping centre on July 27, 1979.

Forty-four years later, momentum is building behind a push to excavate the sand dunes at Primbee in search of the girls' remains.

Dakers is calling on police to declare the site a crime scene, believing the backpacker murderer Ivan Milat may have killed the girls and buried them there.

Experts have long theorised that Milat must have had more victims than the seven he was imprisoned for torturing and killing, making the late serial killer the go-to suspect for countless unsolved disappearances along Australia's eastern seaboard.

But no one knows where to look for those bodies.

Dakers says he has a witness who is pointing him, compellingly, towards the sand dunes at Primbee.

People walk their dogs on what's left of the shabby old paths there; kids ride through on bikes. But are they dancing on a killing field?

Dakers' Food Hub work brought him into contact with the man who would become his witness about three years ago.

After Dakers shared details of his police past, the man told him he had lived on Windang Road and played in the dunes as a boy.

He said he was 12 or 13 when he visited the dunes one day and saw a man with two girls who were screaming out, 'he's going to kill us, he's going to kill us'.

He claims he told the girls to "run in different directions - he can't chase you both at once", and later learned the girls had made it safely to a neighbour's house on Windang Road.

Returning to the dunes weeks or months later, he alleges he saw the same man with his ute reversed up against a sand dune, and a shovel in hand. This time the boy fled against the sound of the man's ute seemingly revving in pursuit.

"He looked at him and got a bit worried, having previously recognised him," Dakers said.

"While he did that, this ute roared up. He felt like the car was chasing him. He was concerned about his own welfare and pedalled quite quickly and got through a hole in the cyclone wire fence onto the [neighbouring] golf course."

The witness has told Dakers the man's ute had a bullet-sized hole in it, and that there were road works in the area at the time, involving the same type of machine he later learned Milat was known to work on. He said he identified the man as Milat, who was believed to be working as part of a road gang, after seeing him on the television years afterwards.

"He wouldn't have realised who he was at the time, because [Milat's crimes] didn't come out until the eighties ... He was just a nobody," Dakers said.

Dakers' witness has also reported seeing a shed in the dunes area - since believed collapsed - with its floor "covered in blood".

The dunes are off Bakers Lane, home to an old radio tower and the site of what was once an effluent dump.

The witness has offered to personally foot the bill for excavating the site, telling Dakers he is confident he could find the exact spot if only he could clear some of the vegetation.

Read more: Lost human remains of Aussie WWII soldiers recovered from Kokoda Track

What has motivated Dakers so much - at 71 years old, he seems on the brink of picking up a shovel himself - is the man's status as a "reliable informant". He describes the witness as a businessman who employs several people, a man with no motivation to lie or embellish.

"Because of the credibility of the witness. ... it should really be declared a crime scene. Especially when we've got some really good strong potential locations in an area for a possible dig down there with a machine," Dakers said.

"What he wants to do is push back some of this [vegetation] so he can reevaluate and familiarise himself with what it would look like back in the day.

"I believe him. The quality of the witness cannot be ignored. Even if we don't end up finding anything, I believe him."

Dakers is protective of his witness and refuses any media introductions. But he convinced the man to sit down for a police interview about a year ago.

He is frustrated that nothing came of that interview. He believes the information was forwarded to NSW Police's crime squad in Sydney, but was later told by police that the tip was dismissed because it "didn't fit with Milat's modus operandi".

"Milat didn't come out until the 1980s - he didn't have a modus operandi yet," he said, noting Milat would have been 34 in 1979. "That sort of brought the whole thing to a halt. But it's not rocket science. He had to have started somewhere.

"A lot of cops have one case that grinds them. This one grinds me."

In the meantime, Dakers has produced a video for police, recording himself explaining maps, walking into the scrub and driving the approximate three-minute journey from the bus stop to where Bakers Lane gives way to scrub.

During the short drive, he shares a theory on how easy it would have been for Milat to slip off Windang Road onto the secluded Bakers Lane, perhaps telling the girls - if there were visible roadworks - "I know a shortcut".

Dakers recently met with NSW Homicide Squad Detective Chief Inspector David Laidlaw to make his case for acting on his witness' claims.

Insp Laidlaw told the Mercury Milat's involvement in the girls' disappearance could neither be ruled in or out.

"It would be premature for me to say anything at this stage," he said.

"We'd have to assess what the information is.

"A lot of it comes down to the legitimacy of the information, assessing it. We'd certainly have to seek some sort of order whether it be by the coroner or otherwise, an order to conduct an excavation on public land."

Milat reportedly worked in Kiama at one time, and was known to have travelled on Shellharbour Road. The Mercury has been unable to verify if this was at the time of the girls' disappearances.

He succumbed to oesophageal cancer in Long Bay Correctional Centre in October 2019, having rebuffed all invitations to confess, instead maintaining he was innocent of any unsolved murders, or any of the killings he spent 25 years in prison for.

Before he died, he left instructions for some of his remains to be scattered in the Illawarra.

"We had a family farewell with about 10 of us down Wollongong way, at a little inlet,' Alistair Shipsey, Milat's nephew, told Daily Mail Australia at the time.

"He told us in a letter that he wanted us to scatter them down the South Coast near the ocean and for Bill, the brother he was closest to, to keep some."

The Daily Telegraph has since reported that the ashes were scattered off Sea Cliff Bridge at Otford.

Kay Docherty's twin brother Kevin had mixed feelings when he learned Milat had died.

NSW detectives working on the Milat murders had visited him in 1996, the same year the Belanglo serial killer was convicted of having murdered seven young people between 1989 and 1992.

"I think he [Milat] has done a lot more than anyone could imagine, and more than he's ever admitted," Mr Docherty said.

"I've always thought this guy doesn't deserve to breathe the air we live in, but my other thought when he died was, 'bugger, he's gone. We're not going to get anything else'.

"Sometimes I think that's the way police think too: 'Milat's gone, he's dead and buried, we're not going to bring this back up'. But just walk in our shoes. Just for a few days or a week or a month - let alone 40 years.

"There's nothing worse than not knowing, all the years you've been robbed of having a sibling. So it does matter. It matters so we can put things to rest."

Visiting the sand dunes, a five minute drive from the family home he and Kay grew up in - the home he has never been able to leave because it is his last link to his forever-young sister - he lets himself wonder if she is close.

"It's pretty eerie," he says, surveying a clearing in the scrub.

"And when I think of it, the more I think about it, the more I think it was possible."

Mr Docherty has been contacted frequently over the past four decades by well-meaning but sometimes misguided people wanting to help find his sister.

Read more: 'Safe, high quality': Aussie growers deny poisonous mushroom claims

It often stirs a complicated and painful cycle of hope and disappointment.

But he is buoyed by the emergence of Dakers' witness and wants to see the dunes excavated.

"This guy is a businessman, he's not interested in the reward. He didn't want the publicity, and he's willing to fund the dig," he said.

"If he's willing to go as far as he has and he's willing to put machines in here, surely there must be something there. Surely he's not going to waste his time and energy and his money."

A 2013 inquest into Kay and Toni's disappearance found the initial police investigation was ''scant at best'', with police at the time dismissing the pair as ''runaways'' - a description that still stings for Mr Docherty.

The first newspaper article alerting the public to the girls' disappearance was published in March 1981 - 20 months later. In the meantime, it fell mostly to Kay's mother to search for her daughter.

"I've never put the police down because I know it's gonna be one of the toughest jobs in the world, what they do, with limited resources," Mr Docherty said.

"But my mum had to do all the searching. Make all the phone calls. Go to all these cults, go to all these religious places in Sydney. It 100 per cent wasn't handled properly.

"An officer just said, 'go home, she's a runaway'. I'll never forget them words."

Both the Dochertys and Cavanaghs received letters supposedly written by the girls in the weeks after they vanished, assuring their families they were OK and that they would be home soon.

The Dochertys supplied police with the letter's envelope in the hope it would yield a fingerprint, only to receive an apology years later - police had lost that piece of evidence.

Mr Docherty was positive when new investigators were assigned to the case in 2004 and remains glad that his mother Jean was still alive to see them chasing down hundreds of leads.

"But I still think they were limited in what they could do and what they had to work with. I think at the end of the day, they were going through a lot of these cases because they had to start to eliminate them and start getting them to the coroner's inquest," he said.

"I think there was boxes being ticked. You learn that some information has made it to Crime Stoppers, but seemingly not much further."

Time has transformed the dunes at Primbee. The thicker vegetation and the vanished paths have made it a darker, more mysterious place. And yet sand yields even to a shoe toe.

If the unthinkable has happened, and those mounds hold a black secret, it is there for the taking.

With thanks to Wollongong Library Local Studies section