Australian Prime Minister Harold Holt disappeared while swimming in December, 1967. Presumed drowned, later explanations included the CIA, China, and UFOs.
YOUNG MAN IN A HURRY
Harold Holt was born in Sydney in 1908.
His father was a theatre manager and the family moved around, following his work, having stints in regional New South Wales and Adelaide before settling in Melbourne. There, Holt attended Wesley College, where he distinguished himself as a scholar and sportsman.
This continued at the University of Melbourne, where Holt studied law on a scholarship. He was top of his class, captained the school cricket and football teams, and starred on the debate team.
Holt was a popular student, but was also viewed as a ruthless, ambitious young man. His driven nature has often been attributed to his parents; his mother died when Harold was 8 and his father was a remote figure, leaving the care of his children to others while he concentrated on his work.
After graduating, Holt passed the Victorian bar in 1932 and went to work as a barrister in Melbourne.
He also joined the United Australia Party (UAP), the leading conservative party in Australia at the time. His smooth good lucks, education and skill as a debater brought him to the attention of the party's leadership, who saw him an obvious candidate for elected office.
He was selected as a UAP candidate in the Federal election of 1934, and again in the state election of 1935. But neither run was successful.
Despite these setbacks, the UAP viewed Holt as one of their rising stars and eventually offered the young go-getter the safe seat of Fawkner. Elected to Federal Parliament at the age of 27, Harold Holt remains one of Australia's youngest ever MP's.
BOB MENZIES & THE RISE TO THE TOP
Joining the UAP in the same year as Holt, but 14 years his senior, was another man destined for the top of Australian politics; Robert Menzies.
Menzies and Holt had very different personalities - Holt slick and conciliatory, Menzies gruff and bullish - but shared many policy positions, and a fierce work ethic. They both had a love of the theatre, which helped cement their unlikely friendship.
With the sudden death of Prime Minister Joseph Lyons in 1939, Menzies (made deputy leader only the year before) assumed the Prime Minster-ship in dramatic circumstances. Menzies immediately reshuffled his cabinet, and continued Holt's rapid rise by promoting him to the Ministry (as Minister without Portfolio).
But Menzies' blustering style made enemies within the UAP as well, and he was forced to resign in 1941 after a vote of no confidence. Surprisingly, Holt was one of the members who voted against Menzies, although he never revealed his reason and the two would remain friends.
Ongoing tensions within the UAP would eventually lead the party to splinter and, finally, to dissolve, in 1944. In the space this created on the Conservative side of politics, Menzies formed a new party, The Liberal Party. One of the Liberals first members was Harold Holt, who joined the Prahran branch shortly after it was founded.
Menzies lead his new party to election victory in 1949, ushering in 23 years of Liberal rule.
By this time, Holt was one of the highest profile members of the Liberals, and was already being touted as a future leader. Over the next decade, Holt would serve in a variety of positions, including Minister for Labour, Immigration and National Service. In 1958 he succeeded Arthur Fadden as Treasurer, the traditional role for the heir apparent.
But he had a long wait.
Menzies did not retire until 1966, with Holt sworn in as the 26th Prime Minster on Australia Day of that year.
ALL THE WAY WITH LBJ
As Prime Minster, Holt largely continued with the policies of the Menzies era, although he modulated some aspects.
But Holt is perhaps best remembered for his personal friendship with American President Lyndon Johnson, and his resulting decision to escalate Australia's involvement in the Vietnam war.
The two men were known to each other from before Holt became Prime Minister, and they renewed their friendship when Holt visited Washington in July 1966.
They shared a similar background and temperament, and became so close that Holt's wife would describe their relationship as 'spectacular.' It was on this visit that Holt made his most famous remark; asked to describe US-Australia relations, Holt said Australia would go 'all the way with LBJ'.
Johnson's return visit to Australia in October 1966 was less cordial, with violent demonstrations dogging the President's itinerary.
But despite the controversy attached to Johnson, and the Vietnam war, Holt's government remained popular. At the 1966 election, the Liberal Party recorded a massive 57% of the two party preferred vote, the highest in Australian political history.
MISSING IN THE SURF
On December 17, 1967, Holt rose early and drove down to the Mornington Peninsula. An avid sailor, Holt wanted to watch solo around the world yachtsman Alec Rose enter Port Phillip Bay.
With the Prime Minister were some friends, and two bodyguards. After Rose had sailed by, the small party made their way to Cheviot Beach for lunch.
It was a broiling day and, always a keen swimmer, Holt decided to take a dip after lunch.
His companions tried to dissuade him. The surf was rough and Holt's health - he had collapsed in Parliament earlier in the year - had been in doubt.
But the Prime Minster was determined. He had a holiday house nearby and knew the local ocean conditions well. He dismissed concerns about the rough sea and changed into his bathing suit, before striding into the ocean.
He quickly swam out past the breakers.
'It was a very hot day. And the surf was extremely turbulent. It was beserk.
Harold went in first. And I thought, I'll have a dip as well.
I went in and I felt this incredible undertow, likely to sweep me out to sea.
I got out and then I saw that Mary was quite agitated.'
- Alan Stewart, eyewitness
The Mary mentioned above was Mary Henderson, a family friend of Holt's who was along for the day. She had reportedly seen Holt dip below the waves, and had then not been able to spot him afterwards.
Other witnesses said they had seen Holt turn around and make for shore, before disappearing from sight.
The alarm was immediately raised.
Within an hour helicopters were scouring the waves, and by sunset more than 200 search personnel were involved. The largest search in Australia's history would last for three weeks, and involve members of the Army, Navy and Coast Guard.
But after two fruitless days, those involved knew that the best they could hope for was to find the PMs body.
Holt was pronounced dead on December 19, and National Party leader John McEwan sworn in as Prime Minister the same day. On December 22 a memorial service was held for Holt, attended by 19 heads of state from around the world, Holt's good friend Lyndon Johnson among them.
No trace of Holt's body has ever been found.
THE CIA, THE COMMUNISTS, AND MAYBE UFOs
But the absence of a body, and Holt's personal history, soon brought forth some alternative theories.
In 1970, paranormal investigator John Keel wrote 'Operation Trojan Horse', a widely read book that claimed that aliens were behind a number of unsolved mysteries from history. Keel claimed that Holt had, in fact, been abducted by aliens; just the latest example of their regular intervention in human affairs.
Later, in 1983, British journalist Anthony Grey wrote a best selling book that claimed Holt was actually a spy, working for the People's Republic of China. In this telling, Holt hadn't drowned but had actually learned that his cover was about to be blown, and had arranged to be collected by a Chinese submarine.
Another popular theory posited that Holt was actually a CIA agent; how else to explain his enthusiasm for the Vietnam war? In this story, Holt has had a change of heart, and wants out of the conflict, and is subsequently assassinated by US government agents.
Still others thought that Holt had simply become depressed, and committed suicide.
In 2005 the Victorian Coroner, who had not previously investigated due to the absence of a body, conducted a formal inquiry.
Their conclusion was that Holt had accidentally drowned; a tragic case of an experienced swimmer overwhelmed by freak conditions. The report speculated that Holt's body may have been swept from the area by strong currents, or eaten by sharks, both common enough in the Southern Ocean.
While this put an official end to the matter, the lack of a body means that for some, this mystery can never be solved.
Holt remains the only Australian PM to die of unnatural causes while in office. Swimming is now banned on Cheviot Beach.