When the Australian Prime Minister Harold Holt disappeared into the sea off Cheviot Beach in December 1967, there was no shortage of conspiracy theories as to his whereabouts.

Everyone had their pet theory, from espionage to kidnapping.  Forty years after the event, the National Archives of Australia has gathered a selection of letters expressing such ideas and placed them online as their September/October Find of the Month.

‘These theories came from around the world,’ said curator Tracey Clarke from the National Archives.  ‘It’s surprising to see how many people took the time to write and express their views on the matter.’

The day after the prime minister’s disappearance an American attorney-at-law wrote to Australia, outlining his own ideas. He believed Mr Holt’s death ‘resulted from expert sabotage’. He requested that his letter be viewed as ‘top secret’ and passed to the Australian government’s ‘top investigative agency’.

‘The people of Australia also had their views on the matter and weren’t afraid to put them in writing,’ said Ms Clarke. ‘Many clung to the view that Mr Holt was still alive somewhere.’

Retired school teacher Miss W. Shonham of Randwick wrote expressing her concern about the ‘disappearance of our dear Mr Holt’.  Her view was that Mr Holt had been ‘kidnapped and taken away by submarine and is being brain-washed for political information’.

But others assumed the worse.

A Ceylonese astrologer D. Dharman wrote to the acting prime minister ‘Most respected and honoured sir’, expressing his sympathy to the government of Australia.  He also advised that he was ‘in a position to announce the present position and the whereabouts of the body’.

In January 1968 a joint report by the Commonwealth and Victorian police concluded that Mr Holt’s disappearance was accidental, but the report did not determine the cause of his death. And it didn’t squash the rumours which continued to circulate. It was not until 2005, when a Victorian coronial inquest found Holt accidentally drowned in heavy surf, that the myths surrounding his disappearance were finally dispelled.

The see Find of the Month. Visitors to the Archives Canberra head office can also see items pertaining to Harold Holt’s disappearance on display.