Under the Australian Constitution, who will become Australia's Head of State if the British monarchy is suddenly dissolved or overthrown and Britain becomes a republic?
Australia calls Elisabeth II "Her Majesty Elizabeth the Second, by the Grace of God, Queen of Australia and Her other Realms and Territories, Head of the Commonwealth." This formula does not mention that the Queen of Australia is also Queen of England. If the British ruling dynasty is overthrown in one of her realms, in theory that does not affect her standing in the other realms.
In practice England is not quite comparable to the other realms of the Queen.