Updated

A court battle has begun over the possible release of secret letters revealing what Queen Elizabeth II knew of her Australian representative's stunning plan to dismiss Australia's government in 1975.

Historian Jenny Hocking asked the nation's Federal Court on Monday to force the National Archives of Australia to release the letters between the British monarch and her former Australian representative, Governor-General Sir John Kerr. The Archives has 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.