More than 200 letters were sent between Queen Elizabeth II and the Governor-General Sir John Kerr during 1975 at the height of the Gough Whitlam dismissal. The letters were then locked away in the National Archives of Australia for 31 years before they could be publicly released.

When 2006 came, however, the record-keeping agency would not release the sealed correspondence, known as the Palace letters, as they had been deemed personal and subject to the Queen's 2027 embargo.

This led historian Professor Jenny Hocking on a journey that went all the way to the High Court of Australia and one that Antony Whitlam, Gough's son, joined as a pro-bono lawyer.

Mr Whitlam said the idea that the queen and the governor-general could mark correspondence as "personal" and not for the public to scrutinise was "nonsense" in an episode of podcast Seriously Social released on Monday.

"The only time there would ever have been any personal relations with a Governor-General and the monarch was very likely in the war when the queen's brother was the Governor-General," Mr Whitlam said in the podcast.

"They mark correspondences private, but that hardly makes it personal."

Gough Whitlam had been the prime minister for nearly three years but a crucial decision in November 1975 made by then-Governor-General Sir John Kerr would see his term cut suddenly short. An opposition caretaker government was put in place before an election the following month delivered a Liberal Party landslide.

The correspondence between the Queen and the Governor-General at that time was stored and sealed in the National Archives for three decades, raising suggestions she might have played a part in the decision. When the royal family pushed back on releasing the letters publicly after the 31 year deadline was up, those question marks remained.

"Very early on in the litigation, there was evidence put on by current officials in the royal household, the existing private secretary to the Queen, saying that they regarded as most important that any correspondence between the monarch and any of the vice-regal representatives and several other rungs of the Commonwealth, should not be made public," Mr Whitlam said.

"Of course, the difficulty then was that was just contrary to the legislation in this country."

The letters were finally released in July 2020 after a lengthy court battle but did not contain evidence the Queen had played a part in Whitlam's removal as prime minister. What they did show, however, was that Sir Kerr had been canvassing about the removal for some time earlier than initially expected.

"What was the interesting part was how early in the piece the Governor-General had been canvassing propositions about his possible exercise of this power to dismiss the government from very early on during his office," Mr Whitlam said.

"It's some alarming predisposition on his part, quite apart from what eventually transpired in the houses of parliament in 1975."

Professor Hocking, who has released The Palace Letters on the events, said her research into letters has since made her feel sorry for Sir Kerr.

"He had become a captive of the decisions he had made that he was, in many respects, certainly by the leader of the opposition, cajoled and urged and threatened in Malcolm Fraser's own words to make," Professor Hocking said.

"This is a very disturbing element in the history is how much pressure Kerr was placed under."

Transparency was eventually achieved but it's all come at a great sum to the taxpayer's purse. Professor Hocking said the cost of getting to the bottom of the 45-year-old crisis has cost the National Archives around $2 million.

"There's been real challenges to all public collecting institutions because of funding cuts and the Archives has been no different from that," Professor Hocking said.

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"There's been a significant complaint and a consistent one about the delays in accessing records, so I put that as the context to a decision by the Archives to make the sorts of resource decisions and expenditure decisions in contesting this case all the way to the High Court.

"The total cost for the Archives now is probably closer to $2 million, we estimate, and that will come out in their own reporting on that.

"It's a really significant sum."