Australia's constitutions tell only part of the story. They omit or barely mention many of the essential and well-known elements of the system of government, such as the cabinet, the prime minister or premier, ministerial responsibility or the opposition.

The difference between what exists on paper and what occurs in practice arises from binding, yet unwritten constitutional rules or 'constitutional conventions'. This is a subject that has given rise to much misunderstanding but on which little has been written in Australia, despite the critical role of conventions in systems of...