The notorious cold case, which saw Jane, 9, Arnna, 7 and Grant, 4, go missing after a trip to Glenelg beach, South Australia, on Australia Day, 1966, has now been blown wide open in an explosive new investigation sparked by Seven News Investigates.
It has been one of the nation's most captivating mysteries, and there are now hopes it is about to be solved.
Dr Mallett is a criminologist and forensic anthropologist. Initially Dr Mallett was ‘cynical’ about the possibility of breaking new ground on the case.
'I thought we were going to rehash all the old information,' Dr Mallett told the Newcastle Star. 'So much work had already been done.'
During the research stage of the project, two men aged in their 60s were questioned about a rectangular hole they dug for a well known Glenelg businessman Harry Phipps the weekend the children went missing.
At the time of the crime the men were aged 15 and 17. It was only after the publication of the 2013 book The Satin Man: Uncovering the Mystery of the Beaumont Children, in which Mr Phipps was named, they realised their information might be of value.
Dr Mallett also told The Advertiser that if Phipps were to have murdered the Beaumont children it is highly likely that he would have killed again - casting attention on other child disappearances that occurred in following years.
'I do think that whoever took these kids is unlikely to have stopped,' Dr Mallett said. 'We do know that most people who are sex predators think about it for a long time.
'We know with paedophiles that they start thinking about and fantasising in their youth and think about their crime for years and years.
'So if this is something they have been thinking about for a long time, the likelihood of them acting and then stopping is quite small. I don’t think it was a one off and I would be very surprised if the person stopped.'
The Seven News investigation will air on Wednesday, Jan 31 at 9pm.
This article originally appeared on New Idea.