A historian has been granted special leave to appeal to the High Court as she fights for the public release of letters between the Queen and the governor-general who dismissed prime minister Gough Whitlam.

The so-called palace letters between Buckingham Palace and Sir John Kerr in the months before the 1975 dismissal have been deemed personal communications by the National Archives of Australia and the Federal Court.

But Professor Jenny Hocking says it's a matter of principle that Australians be able to access documents critical to their history.

Her legal team on Friday argued the letters were made for the purpose of Sir John performing his role as governor-general and therefore were the property of the Commonwealth.

Bret Walker SC said if the letters were considered private, the "records of our governors-general" were capable of being sold to a private collector and held in a vault in Geneva.

That outcome was "absurd", he said.

The letters are held by the national archives after Sir John gave them to the institution.

They are embargoed until at least 2027, but the Queen holds a final veto over their release.