A couple of weeks ago I marked a pile of essays addressing the question "What role does the media play in liberal democracies?" The students enthusiastically recapped the history of the premise that the media is the fourth estate, the defender of the separation of the powers and democracy’s watchdog.

Last week, 16 police officers raided Perth's Sunday Times newsroom. They weren’t investigating the paper, it had done nothing wrong. They were looking for clues about the identity of someone who spoke to a journalist about "secret government business", business so secret it qualified for protection under the section of the criminal code that deals with "Disclosing official secrets".