Letters written by the Queen before the 1975 dismissal of then Australian Prime Minister Gough Whitlam can be made public, the Australian High Court has ruled.
Mr Whitlam’s government was removed by her representative at the time, Governor-General Sir John Kerr, and replaced with an opposition party.
The dismissal is often described as the most controversial episode in Australian political history.
It is not known what the letters between the Queen and Sir John contain.
Historians have long questioned what Buckingham Palace knew about the removal of Mr Whitlam, a progressive whose reforms divided Australia after two decades of conservative rule.
More than 200 letters have been kept sealed in the National Archives since 1978, but on Friday the High Court of Australia ruled they could be accessed in the national interest.
It follows a challenge by historian Prof Jenny Hocking to have them released as state records – documents which are disclosed after a 31-year embargo.
What happened to Gough Whitlam?
Mr Whitlam and his Labor Party came to power in 1972, implementing policies which many celebrated, but he grew less popular amid a troubled economy and a fierce political opposition.
On 11 November 1975, he was sacked on the justification that he had failed to get parliament to approve a national budget and then subsequently declined to resign or call an election.
As Australia is a constitutional monarchy with the Queen as head of state, the governor-general had the authority to do this.
But it was an unprecedented action which shocked the country and prompted questions about Australia’s political independence.
Some viewed it as a “constitutional coup”, sparking strikes and violent demonstrations as well as discussion about the country becoming a republic.
But others celebrated his departure. In a general election held a few months later, voters overwhelmingly elected Malcolm Fraser’s centre-right Liberal Party – which had been acting as a caretaker government.
What are the letters?
The collection of letters, dating from before and after the dismissal, are between Sir John, the Queen, and her personal secretary.
On Friday, Prof Hocking welcomed the court’s 6-1 majority ruling as an “important decision” for all Australians.
Prof Hocking has previously told the BBC she believes the letters will reveal whether there was influence on Sir John’s decision.
She plans to travel from Melbourne to Canberra to access the letters once coronavirus-related travel restrictions are lifted, local media reported.
Her legal challenge, which initially failed in a lower court last year, had been crowdfunded by a “Release the Palace Letters” campaign.