Clifford Bartholomew murdered his wife and 7 children. Then he had a second family.

When then-Detective Allen Arthur arrived at a remote Hope Forest farm, 40km south of Adelaide on September 7, 1971, he walked into the home's kitchen to find a man at the table calmly drinking a beer.

Scattered around him, across the property, were the bodies of his family.

Only 30 minutes earlier, Arthur had received a frantic call.

"It was the early hours of the morning [and] Detective Sergeant Giles rang, and from memory it was still dark," a now 85-year-old Arthur told Mamamia's True Crime Conversations.

"He said, 'We've got a job on; they've got 10 people dead.'"

Listen to the story of Australia's worst family mass murderer. Post continues below.

The man at the table was 40-year-old Clifford Bartholomew, who had just murdered his wife Heather, as well as his seven children aged between four and 19, his sister-in-law Winnis, and her 19-month-old son, Daniel.

"When I spoke to him, he spoke pleasantly, so to speak," Arthur recalled. "He didn't show any signs of distraught. Cool, calm, and collected was the only way I can describe him having just killed 10 people, which surprised me to a point.

"But once I got to know him, it was easy to understand that he just was able to do things and not get too flushed about it," he said.

To date, it remains the deadliest mass family murder in Australian history. Yet most won't know his name, let alone remember the names of his victims.

Heather, 40, (left) was murdered alongside her seven children. Pictured from top left; Christine, 17, Sharon, 15, Gregory, 10, Roger, 7, Helen, 13. (Not pictured, siblings Neville, 19 and Sandra, 4). Image: Find A Grave.

Winnis, 26, and son Daniel, 19-months. Image: Find A Grave.

"It made headlines at the time," former Adelaide Advertiser journalist Craig Cook told True Crime Conversations.

"Adelaide is known for a lot of murders and mysteries, [and] this one kind of definitely disappeared from the public consciousness. I can't find a friend who remembers it. It definitely just got lost, I think."

Bartholomew was released from prison after just eight years. As the murders had dropped out of public memory, he was able to craft an entirely new life for himself — one as a step-father to seven kids who had no idea he'd previously killed his children.

"It's been 54 years. These murders are still fresh in my mind."

When Arthur had arrived at the scene of the crime, he came across Winnis' body outside the home. She'd tried to flee.

It was just hours after a Father's Day celebration at the farmstead that was supposed to bring the estranged family together.

Inside, Heather's body was found in the master bedroom. Her daughter Sandra was in bed next to her, just four years old before her death.

Clifford Bartholomew killed 10 members of his family in 1971. Image: Adelaide Advertiser.

The rest of the children's bodies were found scattered around the house; in hallways, on bedroom floors and in their beds.

Neville, 19, Christine, 17, Sharon, 15, Helen, 13, Gregory, 10, Roger, seven, Sandra, four and Daniel, 19-months, were all shot — as were Heather and Winnis. Many of the victims were bludgeoned with a rubber mallet, too.

"I can never forgive him. Never," Arthur told True Crime Conversations.

"It's unforgivable what he did when it came to children," he continued. "I mean, a two-year-old baby in a cot…[he] puts the gun to its head and kills. I mean, goodness gracious me. It's not normal, but it was for him."

As Cook added, the death of baby Daniel was particularly sinister because, "he went to the kitchen table, sat down, started drinking heavily, but after about 30 minutes, he realised the baby was still asleep in the cot, and he went back, and he put a bullet in that baby's head… that's why they call him a monster."

Of all the cases Arthur worked on as a detective, this is one he can't forget. To this day, he keeps the crime scene photos in his house — he can't bear to get rid of them.

"I have one wish for his soul: that he rot. I have no sympathy for this man whatsoever. I mean, it's now 54 years since these murders occurred…. they're still quite fresh in my mind and will persist until I pass away," he said.

Once Bartholomew was arrested, he admitted everything. He told police that he had only meant to kill his wife, who he suspected was having an affair. But, as he told police, "Once I had shot Christine (his eldest daughter), I realised I had to kill them all. I couldn't leave any behind. I loved them all too much".

Initially, Bartholomew was sentenced to death. However, he was only convicted for the murder of Heather, because the prosecution could prove premeditation and that crime carried a mandatory death sentence.

As Arthur explained to True Crime Conversations, "I only charged him with the one that we had the most evidence about, because irrespective of whether you charged him with 10, he's only going to get the same time in jail. So that was the one that the proof was in abundance, whereas [with] the others, there might have been excuses for rage and mental problems and so forth, [but he] was admitting freely to having wanted to murder his wife."

In the mid-1970s, the Dunstan government abolished the death penalty, and Bartholomew's death sentence was changed to one of life imprisonment. Somehow, he made parole within eight years of the murders.

Cook was able to track down the file that detailed the reason Bartholomew was released on parole. It was just one sheet of paper.

"The piece of paper basically implies that he had mental issues at the time, depression, and that the psychologist's report suggested he would never do this ever again, which is quite leap… but that was the logic," Cook said.

"The other thing that came through was that this was considered a domestic violence incident, and therefore, 'lesser'. If he'd killed 10 strangers, there's no way he would have been out of prison, but he killed his own family, and therefore some kind of logic suggests that he's not a threat to anybody else," he told True Crime Conversations.

So Bartholomew was released in 1979, free to have another crack at life as a free man.

He lived undisturbed and undiscovered for the rest of his life.

Uncovering Clifford's second 'secret' family.

Craig Cook first learnt of Clifford Bartholomew in 2018, when his editor at the Adelaide Advertiser sidled up to his desk, dropping a dusty paper and some photographs in front of him. It was, of course, the details of the horrific Hope Valley murders.

"I just had never heard of them…it was unbelievable," he told True Crime Conversations. He asked his colleagues about the case, and they were equally bewildered.

Watch: Craig Cook on discovering this story. Post continues.

Soon, Cook tracked down Bartholomew's niece, Winnis' daughter. She told Cook that she'd been at the family farm on the day of the murders. Her step-brother — sensing that something "wasn't right" at the house — took her home early.

It saved her life, but she spent her adult years terrified 'Uncle Barty' was going to come for her, too. She had no idea what became of him.

"I thought I owed it to her to tell her if he was dead," Cook said.

After some digging, he discovered that Bartholomew had initially moved back to his native suburb of Port Adelaide after being released. But when he received death threats, the decision was made to give him a new identity.

Cook discovered that Bartholomew kept Clifford as his first name, but changed his last name to 'Palmer' and moved to Victoria. Then, he found his grave — Bartholomew had died on November 27, 2002, at the age of 72.

"In loving memories of Clifford Palmer," read the headstone.

"Dearly loved husband of Merlyn. Devoted to and sadly missed by children and grandchildren," it continued.

"[It] was one of the most surprising things I've ever seen," Cook told True Crime Conversations.

He was left even more surprised when he finally tracked down the family, only to discover Bartholomew went on to become a step-father to seven kids of similar ages to his own children at the time of their murders.

After remarrying, he had lived out his retirement in Queensland, happily surrounded by grandchildren. His second wife died in 2012, a decade after him. They were married for 22 years.

"I thought the family handled things magnificently. They had a family conference and told everybody of adult age what was going to be said [in my article]. It was a terrible shock to them all, they just couldn't get their head around it," said Cook.

To them, 'Poppy Cliff' as they called him, was a hardworking, gentle and jovial man who "nobody had a bad word for".

"The whole family enjoyed his company and never saw him raise a fist or even be angry in a situation," they told Cook, with one family member adding that they were "relieved" both he and Merlyn were dead by the time they found out the truth.

As far as Cook could work out, Merlyn and the children were aware he'd murdered his wife (and remember this is the only murder he was convicted for, so the only one on his prison record), but not the children or his sister-in-law and nephew.

Due to the seemingly light sentence he'd received, he was able to explain it as, "a jealous rage" and "a misunderstanding [and he] didn't mean to kill her," said Cook.

What baffles Cook to this day about this case, is the fact it remains so unknown.

Despite how horrible it is.

Despite how much detail there is about the crime and the murderer and the victims.

It has everything needed to ingrain itself in the minds of Australians. But for some strange reason, this particular harrowing crime has fallen through the cracks of time.

Feature image: Find A Grave.