Three-year-old Cheryl Grimmer disappeared from Fairy Meadow beach near Wollongong, south of Sydney, in January 1970.
“I heard this screaming of the kid. That’s what caught my ear,” he said in the latest episode of the Fairy Meadow podcast.
“What was that shrieking sound? I turned around and that’s what I saw.
“When I glanced back at the toilet block, the profile of the guy was sort of full-stride with this baby in his arm, just kind of screaming and yelling at his hip, like low on his hip.”
The Grimmers had only recently moved to the Illawarra region from the UK on that summer day, when Cheryl vanished from outside a shower block.
Witnesses at the time reported seeing an unknown male carrying the toddler towards the car park.
But the potential new eyewitness has added a description to the picture: medium-dark hair, short back and sides and average build.
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The man told the BBC he didn’t go to police at the time because he didn’t know a child had been abducted. His family had only just moved to Australia from eastern Europe and didn’t speak English, he said.
NSW Police told 9News the Homicide Squad was aware of the witness and investigations were continuing.
Former Detective Sergeant Damian Loone said the new potential witness “sounded very credible” and had given permission for a homicide detective to contact him.

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He can’t be named because he was 17 at the time of the disappearance.
At the time, a spokesman for Attorney-General Michael Daley said he’d received the letter and was considering it.