Lord Justice Leveson is said to be no longer enjoying his role as chairman of the inquiry into the "culture, practice and ethics of the press". Little wonder. When it started, his inquiry had all the glamour and drama any criminal judge might want. Hard-nosed hacks squirmed at the questioning of the propriety of their actions. Executives of News International had no alternative but to state their abject apologies for what was done in their name but not, so they said, with their knowledge. Leveson could bask in the assertion of the primacy of the law over an anarchic media.

Now, however, the proceedings have moved from the criminal to the political. David Cameron's opponents want him pinioned with the charge of selling out to Rupert Murdoch, and they see in Leveson a means of doing just that. The emails between the adviser to the Culture Secretary Jeremy Hunt and News International have whetted the appetite. The questioning of Coulson yesterday would, it was hoped, drive the knife still further.

The irony, of course, is that the Prime Minister commissioned the inquiry precisely to avoid this situation. If it hadn't been for his association with Andy Coulson, whom he appointed as his Communications Director soon after the phone-hacking scandal first broke, there would probably have been no inquiry. The question of phone hacking would have been left to the law. But, with Coulson dragging the Prime Minister into the affair, diversionary tactics were employed. The object, as so often with these judicial investigations, was to bury the matter in an endless marshland of general issues about the media and its practices.

It hasn't turned out that way. What Cameron and Leveson seem to have underestimated was the degree of real hatred that there is for Rupert Murdoch, who is seen by some (not without reason) as the source of all the debasement of media standards and the wielder of overweening power over politicians. And so the inquiry has taken the form less of an investigation into an industry than the trial of an all-powerful media magnate.

Time and time again yesterday, the inquiry's QC, Robert Jay, tried to build up a case, almost as prosecuting counsel, that Coulson had been appointed by the Prime Minister as a deliberate move to get the Murdoch press on his side and that Coulson's job was to act as the go-between, a courtier to King Rupert. And if the former showbiz reporter blocked every question with a denial that this was the case, his very defensiveness left the impression that it was otherwise.

Judging from Twitter and other comment as the questioning continued, this is exactly what most people wanted Leveson to achieve: the portrayal of a world in which party leaders and Prime Ministers sought the approval of an overmighty press baron. Looking at Jay's forensic questioning, the QC is clearly not averse to the role of Jack the Giant Killer.

Whether Lord Justice Leveson feels the same way is more uncertain. The problem for him, as for his Committee, is to try to pull the inquiry back from political immediacy and to give shape to its inchoate remit. One doesn't envy him the task, and the press has every reason to fear how he does it.

In a revealing intervention during the Murdoch evidence last week, Lord Justice Leveson declared that every section of society – "including judges" – were made accountable "except the media". Whenever it came to discussing with editors or proprietors the behaviour of the press, there has appeared an assumption, first, that the media is extremely powerful, and, second, that it acts outside the bounds of society, if not the law.

There are many who might agree with him, particularly politicians smarting at the exposure of expenses, and celebrities irritated at revelations about their lives. But the assumption begs a host of questions about whether a press in rapid decline does have this power and whether the ethos of a press intent on "discovery" is ever compatible with propriety and privacy.

The trouble with those who want Leveson to bring down Murdoch and all he stands for is that they may well bring about a regulatory regime which judges and politicians would delight in but which would cripple the press as a whole.

The fall of the Murdoch hegemony is an end devoutly to be desired, no doubt. But to usher in a world in which what interests the public is replaced by a "public interest" defined by the establishment would be too high a price to pay for it.

a.hamilton@independent.co.uk