Jenny Hocking won a High Court battle to access letters between the Queen and the governor-general who dismissed Prime Minister Gough Whitlam in November 1975.

The archives said on Tuesday it could take 90 days to release the so-called Palace letters and even then, some parts could remain classified.

"It's enormously disappointing that's their first, immediate reaction," Professor Hocking told AAP.

"I'm very disturbed by that and by what it suggests about the management of the National Archives and the priorities of the National Archives."

The historian's win last month came after a four-year legal battle and a decade since Prof Hocking originally tried to access the 211 letters.

The archives said in a media statement it was working hard to release the documents.

"This requires a thorough examination of the records in consultation with relevant government agencies, to ready them for public release," it said.

Prof Hocking said if any of the letters remained secret, Australians would never know the full history of the dismissal of the Whitlam government.

"If there are any, and I mean, any redactions or exemptions from these letters, I think everybody who follows this would be utterly appalled," she said.

She was also troubled that the archives' statement was released while she was meeting with its director-general David Fricker.

"It was the very matter we were discussing," Prof Hocking said.

The archives and the Federal Court previously decided the letters between the Queen and Sir John Kerr during the time of the dismissal were personal.

That meant they couldn't be released until 2027 and even then, only with the permission of the Queen.

But a majority of the High Court's full bench ruled in May the letters were Commonwealth property.

Buckingham Palace declined to comment on the judgment when contacted by AAP.

Australian Associated Press