On December 17 of that year, Mr Holt went missing in rough seas whilst swimming at a favoured spot, Victoria's Cheviot Beach.
Police soon concluded it was an accidental drowning of an experienced swimmer in dreadful conditions, a theory that was confirmed in a belated Victorian coronial inquest in 2005.
But something did not quite add up for the conspiracy theorists.
A letter from an American lawyer, dated the day after Mr Holt's disappearance, reads: "My hunch from fragmentary press reports is there's a better-than 50 per cent chance that Mr Holt's death was not accidental, but resulted from expert sabotage, probably foreign."