Classical liberal theory views the press as a defender of public interests and a ‘watchdog’ on the workings of government. The term originated in the eighteenth century, gained ground during the nineteenth and even now generates debate.
It is derived from the notion of ‘estates of the realm’. The traditional three are the Lords Spiritual (clergy that sit in the House of Lords), the Lords Temporal (other peers) and the House of Commons. It's been attributed to several thinkers and writers including Edmund Burke, Richard Carlyle and the nineteenth century Times leader writer Henry Reeve. In October 1855 Reeve wrote in an article in the Edinburgh Review ‘journalism is now truly an estate of the realm; more powerful than any of the other estates’ (in Boyce et al., 1978).
The argument runs that the press plays a central but unofficial role in the constitution because it helps to inform the public of issues, articulates public opinion and therefore can guide and act as a check on government. (O'Malley, 1997). But it can only fulfil that function if it is independent and free from censorship.
Described as arrogant and grandiose by some, and satirised in an 1855 novel The Warden by Anthony Trollope, the notion refuses to lie down and die. As one of the ways of expressing the relationship between journalism and society, it still has ideological resonance. As recently as 2001, the BBC's political editor Andrew Marr wrote in the Independent ‘If people don't know about power and let their attention wander completely then those in power will take liberties.’