In this Nine News footage from 18 December 1967, journalists interview Deputy Prime Minister John McEwen and then Treasurer William McMahon as they arrive at Parliament House.

This aerial footage of the Mornington Peninsula, at the mouth of Port Phillip Bay from Portsea to Sorrento, illustrates what a wild piece of coastline it is.

Tony Eggleton was Prime Minister Harold Holt's Press Secretary and close adviser. He was called upon to explain Holt's disappearance during nationally televised press conferences.

Radio and television carried news of Harold Holt’s disappearance on 17 December 1967. This clip is from the documentaryThe Harold Holt Mystery (Ten Network, 1985).

Is Harold Holt still alive? Did he commit suicide? Was he drunk or drugged? Did he secretly belong to a crime syndicate? Was he a Chinese Communist spy?

The search for Holt was exhaustive. Diving teams entered the rough waters repeatedly but were unable to find any evidence or clues to his disappearance.

Zara Holt arrives at Cheviot Beach, the location where her husband had entered the rough sea and disappeared. Holt’s Press Secretary, Tony Eggleton, assists her through the media scrum.

Marjorie Gillespie walks up from the beach.

Did Holt intend to withdraw troops from the war in Vietnam?

Dame Zara Bates was in Canberra when the tragedy happened. She was hastily flown to Melbourne and driven to the Cheviot Beach.