The likelihood of solving the case of the missing Beaumont children — one of South Australia's most enduring mysteries — lessens every year, the state's police commissioner says.
Jane, nine, her sister Arnna, seven, and their brother Grant, four, were last seen leaving their beachside home at Somerton Park for a day at Glenelg Beach on January 26, 1966.
Their father, Grant Alfred Beaumont, died on April 9 this year aged 97.
On Wednesday, Police Commissioner Grant Stevens said Mr Beaumont carried the burden of never knowing his children's fate.
"It's a very sad set of circumstances and there's still speculation as to whether the children may or may not be alive," he said.
"But it's very sad for Grant Beaumont that he passed away not knowing what happened to his children."
Commissioner Stevens said the children's disappearance was an enduring, tragic story in South Australia's history.
"Every year that goes past, I think there is less likelihood of us successfully resolving the Beaumont case," he said.
Commissioner Stevens said evidence collected at the time of the children's disappearance and in the decades since has also had a bearing on the case.
"It's over 50 years now, the reality is the quality of forensic evidence that was collected at that time when the children went missing [as well as] the memory of witnesses, witnesses having passed away — all of these factors contribute to greater difficulties in resolving that particular investigation," he said.
But he said the death of Mr Beaumont did not mean the case was closed.
"The case is still open, and we'll continue to do reviews and we'll assess any further information that is brought to SAPOL," he said.
The last significant investigation into the Beaumont children case involved a dig at a North Plympton factory in 2018.
The task was prompted by two brothers who told police they had dug a hole at the site for deceased businessman Harry Phipps.
He was a person of interest in the case, but not a police suspect.
The unearthing at the factory provided no useful information, but Commissioner Stevens said there remained a "genuine desire" by SAPOL to solve the case of the Beaumont children disappearance.
At the time the children went missing, several witnesses told police they had seen them with a tall, thin-faced man with short, blond hair.
A composite sketch of the suspect was released with hopes of identifying him.
Volunteers helped police in what was the largest scale search in South Australia's history.
Glenelg beach was scoured, drains were flushed and hundreds of witnesses came forward.
Police put out a renewed call for information on the case in 2016, on the 50th anniversary of the children's disappearance.
Their mother and Mr Beaumont's former wife, Nancy Beaumont, died on November 16 of 2019 aged 92.
A funeral notice published last Saturday said Grant — also known as Jim — was "reunited in heaven" with his children.
