The bodies of Karen Edwards, 23, her boyfriend Tim Thomson, 31, and their friend Gordon Twaddle, 21, were found in remote bushland at Spear Creek, north of Mount Isa, in October, 1978.

The friends were just three days into a motorbike trip around Australia when it is believed they were lured into the bush and gunned down.

The Courier-Mail can reveal Bruce John Preston — who admitted to stealing one of the victims’ bikes — also told one of the original investigators he had been travelling the same route as the victims during their ill-fated road trip.

Detectives reinvestigating the mysterious cold case have spoken to Mr Preston as part of their inquiry.

Mr Preston, originally from Mount Isa, now lives in a modest brick home in Goulburn where he worked for many years as a prison guard at the supermax Goulburn Correctional Centre.

Mr Preston was at one stage the head of the elite Special Emergency Response Team at Goulbourn Jail - often referred to as Australia’s most dangerous prison — housing the likes of Anita Cobby’s killers and Ivan Milat. The team is responsible for responding to and quelling riots.

But his social media account shows the former soldier and keen fisherman as a glowing father walking his daughter down the aisle. Military records show Mr Preston as having served between 1976 and 1979.

The Spear Creek case, which is the subject of a true crime podcast produced by The Courier-Mail and The Sunday Mail, is currently being reviewed by the Homicide Cold Case Team.

Detectives have described it as “definitely solvable”.

Karen, Tim and Gordon had planned to travel from Alice Springs, through Mount Isa and across to Cairns, before touring the east coast of Australia, finishing up in Melbourne in time for Christmas.

They set off from Alice Springs on October 2, 1978, on two motorbikes, Tim carrying Karen as his pillion passenger. Tim’s bike, a 1977 BMW R100S, had a homemade sidecar attached that carried the trio’s camping gear and his Doberman pup, Tristie.

Detectives believe the three friends were befriended by another man on a motorbike somewhere between Alice Springs and Mount Isa. They were seen with a fourth man at the Frewena Roadhouse, in Northern Territory. The group of four spent the “heat of the day” playing pool and socialising at the roadhouse.

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The fourth man was still with them when they arrived in Mount Isa on October 4. The three friends paid for two nights accommodation at the Moondarra Caravan Park but were later joined by a man in a brown and white Toyota LandCruiser.

The LandCruiser returned the next morning and collected Karen, Tim and Gordon, leaving their dog Tristie tied up at the campsite. The three friends were never seen alive again.

Witnesses told police the vehicle returned that evening and dismantled the campsite. By October 6, everything but the sidecar had been taken away.

Former homicide detective Jim O’Donnell told The Courier-Mail he was among officers who conducted a raid on Mr Preston’s family home after receiving information Tim’s motorbike might be there.

“(We) went to the address where (a witness) had seen the person who allegedly had the motorbike … and we located the motorbike in the garage,” he said.

“There was also a Toyota LandCruiser located in the garage and police took possession of that. And it was taken back to Mount Isa police station for the examination — fingerprints and whatever.”

Mr O’Donnell said a number of firearms, belonging to Mr Preston’s father, also were taken away for testing. Nothing of value was found.

“We had taken the suspect at that stage back to the police station … where he was interviewed at length on how he came to be in possession of the motorbike,” Mr O’Donnell said.

He said Preston, who last night landed in Brisbane, gave different versions of how he came to have the bike, initially saying he had bought it from someone in Adelaide before claiming he had seen people trying to start it on the side of the road.

He told police — and a subsequent court hearing — he had shouted to the people, who he’d believed were trying to steal the bike, before deciding to steal it himself.

“His story was that he was also doing a trip — from Victoria, up through Alice Springs and across to Mount Isa,” Mr O’Donnell said.

“Initially we believed he was just behind the three deceased persons because the dates he told us were always a couple of days behind.

“He had a motorbike as well. He was obviously a motorbike freak you would say. He was very keen on motorbikes.”

Mr O’Donnell said police had struggled to verify Mr Preston’s movements because he was travelling in remote areas and camping on the side of the road.

“So, after talking to Preston for a period, we got him to write a handwritten statement on just what he told us, just to get something down on paper, and some dates and times and places,” he said.

“Then … arrangements were made for him to come into the police station, where we conducted an official record of interview, which was a typewritten interview.

“And we went through his whole history, about where he’d been and what he’d done … and as much information as we could on where he was travelling and where he stayed in Alice Springs.

“Then we had to try and verify that information.”

Mr O’Donnell said the interview went for many hours and took place over two days. He said Mr Preston spoke to police voluntarily and was “quite open”.

“He was very calm. He wasn’t agitated, he wasn’t nervous. He was very co-operative,” he said. Mr Preston was charged with the theft of Tim’s motorbike and pleaded guilty. He was fined $300.

Mr O’Donnell said he often thought about the case and regrets having not been able to solve it at the time.

He said there was originally a focus on linking the Spear Creek murders with another shooting in Western Australia — involving a mystery man called “George the Moneyman”.

But the fact Karen, Tim and Gordon’s possessions were found at the local tip makes him believe the killer was likely a local.

“I think of the dump … if this was a fellow from Victoria, who just caught up with them for some reason and wanted to murder them, would he know where the dump was? And why would he come in the next day to take them out to show them around town or show them something if he’s a stranger himself, you know?

“A lot of things point to local person. The more you look at everything.”

Described in court reports at the time as an unemployed diesel mechanic, Mr Preston went on to marry, have children and settle in NSW. Last Saturday, he came to the door of his Goulburn home but did not want to talk about the case.

“I’ve got nothing to say to you,” he said, before shutting the door. Mr Preston has in the past denied any knowledge of the killings, telling police he never met the three friends.