Harold Holt was clearly a deeply troubled man when he entered those choppy waters off Cheviot Beach on 17 November 1967, never to return. But was he troubled enough to take his own life, or did he simply not care any more?

The latest revelations really revisit speculation from many years back.

Almost 20 years ago, when I worked at The Age, I was researching a story on the visit to Australia by the US President Lyndon Johnson for Holt’s memorial service in Melbourne. The research yielded two front-page stories: one was that the service was a cover for an allied heads of government meeting to discuss Vietnam; the other was that LBJ “interviewed” all the contenders for Holt’s job.

In the course of that research a then high-ranking foreign diplomat told me how struck he was by Holt’s state of mind just before his death, and he remained convinced that Holt was deeply depressed and took his own life.

Interviews with Holt’s colleagues also revealed a troubled man behind that sunny exterior, but none went so far as to say he took his own life.

Several things were happening to cloud his sky. He had won a stunning electoral victory in 1966 after assuming the prime ministership that year after the retirement of Menzies, but in 1967 it started to unravel badly with a series of government scandals, gross ministerial incompetence and utter treachery by his cabinet colleagues, especially the poisonous and ambitious Billy McMahon.

The war in Vietnam was going badly, and it was creating divisions at home. A meeting with then UK Labor prime minister Harold Wilson that year aroused US suspicions over Australia’s commitment to Vietnam, as Wilson was a critic of the war.

Many years later I exchanged correspondence with Wilson and also talked to him about this, and he confirmed that Holt was under “extraordinary” pressure from the US not to waver.

When I wrote this for The Age the then editor, Creighton Burns, normally a most courageous newspaperman, refused to entertain the notion that Holt’s death was anything but a tragic accident.

“I knew Harold well and this was just not in his nature. It’s fanciful in the extreme,” he said, spiking the story.

When I left The Age to become political editor of the Sunday Herald, then editor Piers Akerman took a similar view when I revisited the story. It simply never saw the light of day.

Holt was decent and well liked – perhaps the last genuinely good bloke to be prime minister. But he moved in a fast set where alcohol flowed like rivers, and partners and lovers were freely shared along with other things that might have constituted a risque lifestyle in 1960s Australia.

That he was about to be named in a divorce case was an open secret, but was that sufficient to drive him to his death?

We will never know for certain what darkness lurked behind that sunny smile.