Chris Smith talks with Harold Holt’s son Sam ahead of Sunday’s anniversary.

On December 17, 1967, Prime Minister Harold Holt went swimming in rough seas at Cheviot Beach in Victoria and was never seen again.

Since that day all kinds of conspiracy theories have formed, suggesting he was taken by a Chinese mini-sub, a shark or even committed suicide.

A report in 1968 and an inquest in 2005 found the death was nothing but accidental.

Harold Holt’s son Sam was 28-years-old at the time and tells Chris Smith about the moment he found out.

“I did hear on the radio that there was a missing VIP at Portsea and I thought well I can only guess who it would be and I can imagine it was my father.

“I ran to the nearest phone box and rang home where our much-loved housekeeper answered and she just said I’m sorry darling he’s gone.”

“He was very cavalier. He would swim where none of us would swim. Our house was never locked, it was never guarded. There was literally no security presence at all.”

Click PLAY below for the full interview