What did the Queen know?

It is a key question which has long hung over the 1975 constitutional crisis, when the Whitlam government was sacked by former governor-general Sir John Kerr.

Key points: Correspondence between the Queen and the governor-general on Gough Whitlam's dismissal remain secret

Correspondence between the Queen and the governor-general on Gough Whitlam's dismissal remain secret The High Court will today hear whether the documents detailing that correspondence are private or belong to the Commonwealth

The High Court will today hear whether the documents detailing that correspondence are private or belong to the Commonwealth Biographer Jenny Hocking has already lost a Federal Court bid to have the papers released

Historian and Whitlam biographer Jenny Hocking has literally taken on the palace in her long quest to find an answer.

Today she has taken her bid to the High Court which she hopes will help to clear the way for her to access to what have become known as the "Palace letters" — correspondence between Sir John Kerr and the Queen during the critical period leading up to Gough Whitlam's dismissal.

She believes the material should not be held from public view, and could hold important information about Australia's history.

"If we have to have secrecy over royal activities then it suggests those royal activities are hiding something that they simply don't want the Australian people to know," she told the ABC's 7.30 report.

"And I think for an autonomous nation that is simply unacceptable."

Outside the High Court Professor Hocking said it had been a long legal process, but she was delighted to have the case heard by the highest legal court in Australia.

"It's about our history, it's about our knowledge of our history, but it's also about having control over our own national archival resources," she said.

"These are really important historical letters that are held in our own national archives … the Queen can see those letters but we can't."

Papers due for release 12 years ago remain secret

The Queen's letters and copies of the letters sent by Sir John Kerr are currently held by the National Archives in Canberra.

The bundle of materials sought by Professor Hocking also includes telegrams and attachments like newspaper clippings, exchanged between August 15, 1974 and December 5, 1977.

The material was deposited by Sir David Smith, the official secretary to the governor-general, in 1978, after Sir John Kerr left the office.

Jenny Hocking says the letters should be classified as Commonwealth records. ( AAP: Peter Rae )

Under the law, Commonwealth documents are released after 30 years. By that measure, all of the letters should have been publicly available by 2008 — but Professor Hocking's efforts to see them have been blocked.

In 2016 the National Archives told her they were "private", rather than "Commonwealth records", and therefore not covered by the rules.

Professor Hocking has already lost a Federal Court bid to overturn that decision. But today, her lawyers will tell the High Court that the documents were created and received by the governor-general as part of his official job and are the property of the Commonwealth.

In submissions to the court, they have cast doubt on the idea that the material was personal.

"[The] evidence did not show that any person who dealt with the records or similar correspondence between a governor-general and the Queen perceived that the Australian copy of those Records was the personal property of the person who was governor-general," the submissions read.

The High Court will also be told there is a constitutional issue if a governor-general were to derive personal property in his communications with the Queen while in office.

Extract of a letter from Sir John Kerr to the Palace dated 20 September, 1975, two months before the dismissal. ( Supplied )

Letters 'aptly described as personal'

Lawyers for the Commonwealth and the National Archives will argue that the letters are not "Commonwealth documents" but were owned personally by Sir John Kerr.

They will tell the court that Commonwealth documents are only those owned by the organisations or institutions of the central government.

In written submissions to the court, the lawyers have also taken aim at the constitutional concerns, saying the governor-general holds an independent office under the constitution, as the Queen's representative.

"Among the multifarious responsibilities of that independent office is corresponding with the Queen," the submissions said.

"The frequency and content of such correspondence is for the governor-general personally to determine."

The submissions also said the letters had nothing to do with the governor-general's exercise of his constitutional duties.

"Such correspondence as does occur is personal, not in the sense that it did not involve in some sense the performance of functions, but because the particular function that as involved for the governor-general is aptly described as personal," they said.

The High Court may be Professor Hocking's best option for getting access to the letters, given the Queen's papers are locked up until 2027.

One thing at stake in the case will be how governors-general should treat their correspondence in future, and just how much of that can be kept private.