Matthew Norman: As ever with Rupert Murdoch, we have an immorality tale worthy of The Godfather

We do not know which version of the mogul will turn up at Leveson. We do know that he will be more reprehensible than his son

Whichever version of himself Rupert Murdoch selects for our entertainment and edification – the doddery amnesiac of the "humblest day of my life", or the defiant paterfamilias grinning the rictus while squiring surrogate daughter Rebekah Brooks to supper in Mayfair – expect to learn nothing about his internal workings from his star turn on the Leveson stage today.

The guide here, as so often with this mob, is The Godfather. "Never let anyone outside the family know what you're thinking," imparts Don Vito Corleone to idiot son Santino (on whose reincarnation in the form of James Murdoch we will touch below). It matters little that the cool and methodical Robert Jay QC will ask all the right questions. Don Rupo will be too well coached to walk into any hidden traps. Last summer's select committee appearance may have reminded you of Sarah Palin's legendary Katie Couric interview. But where she was too indolent and detached to benefit from attempts to prep her for the ordeal, Murdoch père will have mugged up intently, and will keep his inner thoughts to himself.

Every potential question will have been searched for landmines by his lawyers, and the least self-incriminating answers stored away. This is not to suggest that theatre lovers should eschew the live feed in favour of the snooker at The Crucible over on BBC2. I love the hypnotic tranquillity of the green baize as much as the next couch potato, but not enough to miss a moment of the great grotesque's appearance. If this is to be Rupert's public swansong as a figure of titanic malevolence, as seems possible, the beguiling sense of the passing of an era will compensate for any anticlimactic absence of fireworks.

Revenge may be a dish best eaten cold, as Don Corleone says in the film, and if so James had himself a delectable banquet yesterday with the recollection of discussing the BSkyB buyout with David Cameron, assassinating Jeremy Hunt's leadership dreams, and knifing Alex Salmond. God knows what strategic intent the Murdochs had in mind, because spreading the muck to make others stink doesn't improve their aroma a jot. Perhaps, with nothing left to lose, James simply fancied some vindictive fun. He certainly appeared softer yesterday, with the hair grown out and the voice less grating, but maybe the anger management issues evident from his pre-election storming of this newspaper's office to upbraid the editor for not showing Papa enough respect have yet to be addressed?

With Murdoch Snr, who may also feast on some choice refrigerated leftovers today, Schadenfreude seems best eaten straight from the oven. Delicious as it was to see him hamming up the senility while carer-wife Slugger Deng saved him from Johnny Marbles, the passage of time has denuded his decline of its savour. Once the ultimate adrenalin junkie who never felt more alive than when scrambling to avoid catastrophe, at 81 and stripped of his ability to make politicians offers they cannot refuse, it cannot be the elixir it was. Even if the razor-sharp, jackal-charming media lord shows up today, the plain fact of his presence renders this a massively diminished Murdoch Snr. It will depress this paradigm of autocratic arrogance to submit himself to another footling manifestation of li'l old democracy, and outrage him to find himself reduced to a human punchline. The plutocratic powerhouse, for all the residual wealth and power, has become a standing joke everywhere but among his own court sycophants, and ridicule is the most lethal poison in the bloodstream of the terminally self-important. Even Mrs Palin was capable, as those who have seen the HBO biopic Game Change will appreciate, of learning that from Tina Fey.

No one outside the family will learn what Rupert Murdoch is thinking, but you have to assume that the continuing exposure of that family as two-bit mafiosi (the tweet of yesterday came from an ITV News journalist, who at 11.07am reported "Lachlan Murdoch still smiling as he watches his brother James put under pressure") must excruciate so determined a dynast.

James kept his temper, on the surface, but still came across as Sonny (Santino) Corleone, the hot-headed wastrel who desperately wants to succeed his father as Don, but lacks the smarts, and backbone, for the task and lands up sleeping with da fishes. As a film studies dropout (bless him, he couldn't even stay the course at Harvard), James will appreciate this. He may even recognise the grinning Lachlan as Michael, the younger son who is unwilling at first to go into the family firm, but ends up scooping the pot and trying to turn the business legit. There is something undeniably epic about this reworking of the time-honoured immorality tale in which the once mighty but senescent father is brought low by misjudging his issue. If Lear seems too grandiose a template, I refer you to the recent superhero flick Thor. "You are an old man and a fool," the young Norse god yells at Odin. "I was a fool," the All Father morosely replies, before casting the first-born he was about to make king, but whose recklessness has plunged him into unnecessary war, out of Asgard, "for thinking you were ready."

Too frantic bathing his nippers, by his own account, to find time to read the emails that would have alerted him to the scale of phone hacking, James wasn't ready to be king. Frankly, the lad was bloody useless, and Rupert hadn't a clue until it was too late. This stark fact will be underscored today, and while it will make smaller headlines than the revenge visited on the Government by the son, or fresh retaliation meted out by the All Father, it is every inch as important an expression of Leveson's function as unearthing sexier revelations.

This inquiry – impenetrably dull to those not obsessed with what it drily unearths, but endlessly fascinating to those of us who are – is about more than its remit to unravel the truth about hacking and the Met's failure to investigate it, and to examine the wider ethics of the media. It is also, though this is not its conscious intent, about systematically and exhaustively humiliating Rupert Murdoch and his minions – partly for national catharsis, but primarily to obliterate any possibility he or his successors will re-establish poisonous dominion over the political system.

Whichever Rupert Murdoch makes that Frank Sinatra-style positively-final-until-the-next-one appearance cannot reverse that saintly process. Yesterday we saw the slick, well-rehearsed but egregious boy he entrusted with his power. For that, the old man will stand revealed today and forever as an even bigger fool than his son.