Leading article: A light shone into the dark corners of power

Credit where credit is due. As the second phase of the Leveson Inquiry into phone hacking draws to a close, the implications of recent months' revelations can hardly be overstated. Indeed, they entirely explode the myth of Britain as a beacon of transparency and straight-dealing in an often murky world.

The public inquiry into phone hacking and media ethics was, and remains, profoundly flawed. Established in a desperate hurry to shield the Prime Minister from his association with his former press adviser, ex-News of the World editor Andy Coulson, the panel's remit is far too broad and its membership too unrepresentative. Most concerning of all, by running its sessions concurrently with multiple police investigations, the inquiry risks prejudicing any future trials – as at least one former News International executive's lawyer has taken pains to point out.

For all its shortcomings, however, the Leveson Inquiry has made a true and lasting contribution to British public life. While appalling in its details, the first round of hearings focusing on aggrieved individuals from Hugh Grant to the parents of Madeleine McCann held few surprises as to principle. In contrast, the second phase, considering the relationship between the media and the police, has single-handedly rewritten Britain's understanding of itself. The long-held sense that the UK does not suffer from the kind of endemic corruption evident, not just in the baksheesh cultures of the developing world, but in the France of Jacques Chirac and the Italy of Silvio Berlusconi, has been blown to smithereens.

The real hammer blow was testimony from Deputy Assistant Commissioner Sue Akers detailing News International's "culture of illegal payments" feeding "a network of corrupt officials". Not ad-hoc favours. Not the grey area between a boozy lunch and one good turn deserves another. But tens, even hundreds, of thousands of pounds paid to sources in Whitehall, the armed forces, and the police. There was even a system to maintain anonymity.

That journalists or their emissaries hacked into phones or tried to buy information is evidence of a newsroom culture that has lost all sense of proportion, not to mention legality. While inexcusable, however, such behaviour is not so shocking as to force a rethink of basic assumptions about the society we live in. After all, journalists have long ranked with estate agents and politicians near the bottom of the league of trusted professions.

Public officials were a different story – or we thought they were. Not any more. From the bribing of individual officers, all the way up to the loan of a horse (in itself harmless but emblematic of a wider malaise), taking in the cosy dinners, the lucrative PR contracts and the privately organised newsroom internships on the way, the disclosures at the Leveson Inquiry have shone a light into the dark corners of an incestuous world. What has been revealed is a culture of mutual back-scratching and outright corruption that dwarfs even the venality exposed by the MPs' expenses scandal.

It will take more than a single ray of sunlight to sterilise the infection. And it is notable that, of the 40-plus arrests so far, the overwhelming majority have been journalists. So far, the number of public officials on the list does not even make it into double figures – hardly the "network" Ms Akers described. As the police investigation progresses, those who accepted the bribes must be pursued at least as vigorously as those who offered them.

Meanwhile, as the Leveson Inquiry enters a third phase, focused on the world of high politics, it can only be hoped that the testimony of newspaper proprietors and senior politicians will prove equally consequential.