The governor-general who sacked Gough Whitlam thought it best not to explicitly inform the Queen of his move before taking the enormous step on November 11, 1975.
But Sir John Kerr's newly released correspondence with Buckingham Palace shows he did inform the Queen and her private secretary, Sir Martin Charteris, of his thinking in the months before the dismissal.
Following a landmark High Court decision, the National Archives of Australia on Tuesday released details of letters between the then governor-general and the Queen in the lead-up to the dismissal of the Whitlam government.
"I was of the opinion that it was better for Her Majesty not to know in advance," Sir John wrote in a letter on November 11, immediately after sacking Mr Whitlam and making Liberal leader Malcolm Fraser caretaker prime minister.
But archives director-general David Fricker pointed reporters at a briefing in Canberra to a letter from Sir John to the Queen dated September 12, 1975, in which he said Sir John was "describing the contest that's coming".
It included a press clipping which explored the options for dismissal of the Whitlam government.
Sir Martin wrote back referring to the practice that if a parliament refused supply - legislation allowing money to pay for government - it was "constitutionally proper to grant a dissolution" of the parliament.
On October 2, after Sir John had met Prince Charles in Papua New Guinea and discussed his suspicion Mr Whitlam wanted to ask the Queen to remove him as governor-general, Sir Martin told him that if it came to that, the Queen "would have no option but to follow the advice of her prime minister".
Around this time, the Senate made its first moves to block supply and the budget bills bounced back and forth between the two chambers and Mr Whitlam was considering a half-Senate election.
On October 17, Sir John described these events to Sir Martin, including relaying that Mr Fraser was of the view the governor-general had the power to dismiss the government and force an election.
"I do not know what will happen, or what I shall end up by doing, but the country is set on a collision course now of historic proportions," he wrote to the palace.
On November 4, Sir Martin replied with a discussion of the governor-general and Crown's powers to dissolve parliament.
"The fact you have powers is recognised, but it's also clear you will only use them in the last resort, and then only for constitutional and not for political reasons," he wrote.
Sir John informed the Queen, via Sir Martin, immediately on November 11 of his actions in an uncharacteristically short letter of just two pages.
On November 20, he sent a much longer explanation.
The driving force behind the court challenge to release the letters, Monash University's Professor Jenny Hocking, said Sir John overstepped the political line.
"The really startling thing about these letters is the extent to which the governor-general Sir John Kerr is communicating with the Queen about ... political matters that are happening in Australia at the time, about options he may face, and the Queen in response is engaging with that level of conversation at a very political level," she said.
Dr Fricker urged people to read the letters and attachments to get the full context of the historical period, noting that even which press clippings Sir John chose to include gave insight into his thinking.
Buckingham Palace issued a statement saying the letters proved the Queen had no part in the dismissal.
"While the Royal Household believes in the longstanding convention that all conversations between Prime Ministers, Governor Generals and The Queen are private, the release of the letters by the National Archives Australia confirms that neither Her Majesty nor the Royal Household had any part to play in Kerr's decision to dismiss Whitlam," the statement said.
Constitutional law expert Anne Twomey also said the letters disproved conspiracy theories about royal involvement.
"(It) blows away the silly conspiracy theories that we've been having for an awfully long time, which said 'this was all the conspiracy of the British and the establishment and the Queen'," she told the ABC.
It was also revealed the newly sacked Mr Whitlam had phoned Buckingham Palace at 4.15am London time on November 11, as a "private citizen" asking to be recommissioned so he could call an election.
But by that time Sir John had already contacted the palace about the course of events.
Australian Associated Press
