The current affairs output of Channel 4 has been driven by a mischievous agenda ever since its inception. The duty of the channel is to produce, night after night, the unofficial history of Britain. That history is conditional, experimental and profoundly disrespectful of all entrenched opinion and the entire governing class. Channel 4 has no interest at all in the preservation of existing reputations and established power structures.

This is because Channel 4 believes in the limitless potential of the human spirit. It is on the side of the dispossessed, the voiceless and the future. Channel 4’s over-riding duty is to search out voices that have not been heard and truths that have not yet been articulated. The essence of its job is the enfranchisement of the powerless. It is always on the side of minorities.

Channel 4 is the mirror image of the BBC, the only other British broadcaster with a public service remit. The BBC is modern, Channel 4 postmodern. BBC news coverage seeks to be definitive, while Channel 4 is sceptical of any kind of confident assertion. The BBC is reverential of power elites, while Channel 4 scorns them. The BBC looks to answer questions, Channel 4 poses them. The BBC is conservative but Channel 4 justifies its always-precarious existence by taking spectacular risks. It is restless, moving on, always pushing back the boundaries. It is the public duty of Channel 4 to unravel conventional structures of thought, to open up new areas of understanding, and to devise fresh methods of analysis. Channel 4 understands that it must be an instrument of social change, and a vehicle for uncomfortable truth-telling.

But this state of permanent revolution is perilous. There is always the danger that Channel 4 current affairs will take an outlandish line for no reason except perversity. At its worst, the channel can descend into nihilism – a state of mind that contradicts everything it stands for. This is the central dilemma of Channel 4: its constitutional duty to challenge the boundaries of conventional reporting always carries risk of catastrophe.