A legal battle over secret letters revealing what Queen Elizabeth II knew of her Australian representative's stunning plan to dismiss Australia's government in 1975 opened in federal court Monday, in a case that could finally solve a mystery behind the country's most dramatic political crisis.

Historian Jenny Hocking is asking the Federal Court to force the National Archives of Australia to release the letters between the British monarch, who is also Australia's constitutional head of state, and her former Australian representative, Governor-General Sir John Kerr. The Archives have classified the letters as "personal," meaning they might never be made public.

The letters would reveal what, if anything, the queen knew about Kerr's plan to dismiss Prime Minister Gough Whitlam's government in 1975 to resolve a deadlock in Parliament. It is the only time in Australian history that a democratically elected federal government was dismissed on the British monarch's authority. The dismissal stunned Australians and bolstered calls for the country to sever its colonial ties to Britain and become a republic.

Whitlam's own son, lawyer Antony Whitlam, is arguing the case on behalf of Hocking, and took on the case free of charge.

Hocking, a Whitlam biographer, argues that Australians have a right to know the details of their history, and that the letters written in the months leading up to the unprecedented dismissal are key to unraveling the truth.