December 7 — a day of infamy for an empire, its forces tethered and defenceless, the enemy coming out of the sun, laying waste. Yes, all in all a tough day for News International.

This week will be remembered as the one where it all fell apart for what everyone and their mother now calls a criminal conspiracy.

With the Leveson inquiry ploughing on, came news from elsewhere — that private detective Glenn Mulcaire has been arrested again, following last week’s explosive evidence from long-serving scumbag Paul McMullan.

Mulcaire has already done time for the phone-hacking scandal — he was the “detective” who performed the hacking for News of the World royal reporter Clive Goodman, and went to jail for a few months in 2007. McMullan’s evidence explicitly tied Mulcaire to the wider process of hacking at the paper, suggesting that he may face not merely hacking-based charges, but also for perverting the course of justice and worse.

Mulcaire’s arrest will in turn prompt fresh revelations. He has nothing to lose now — he, and others, are facing rather more serious prison sentences than the first time around.

Given that he has accumulated 11,000 pages of notes during his hacking years, it seems more than likely that his final act will open up a fresh round of investigations.

Crucially, the Leveson inquiry has made it clear that Mulcaire was only the technical facilitator of much of the hacking, much of the content part done by News reporters, under the explicit direction of Rebekah Brooks and Andy Coulson.

The latter two are now well in it, and the monolith of News Corp management has cracked down the middle. James Murdoch has now cut Brooks loose, writing to the inquiry to claim that Brooks did not seek authorisation to settle with star-manager Max Clifford — a settlement, including costs, of close to £700,000.

The Brooks-James Murdoch link, or lack thereof, matters because acknowledgement of early knowledge of hacking Clifford’s phone is acknowledgement of the source of dozens of stories about his roster of A-list clients.

Clifford represented not only standard celebs, but tragedy-afflicted civilians eager to fight off the tabloid media, or f-ck it, or both. He was the mother lode for NotW, and the settlement with him a clear indication of a generalised hacking.

Cutting Brooks loose is the nuclear option. It was used on Coulson too — and he has now responded by launching a legal suit against News Corp, claiming there was an agreement in place that News would pay Coulson’s legal costs.

Even the good news is bad news for News. Now, ex-deputy editor of NotW Neville Thurlbeck has written to the Commons committee (media, privacy gambling, the Orkneys and badgers, or something) to claim that there was active withholding of evidence from the police. Thurlbeck was the intended recipient of the “for Neville” email, which covered the transfer of transcripts in the NotW office, thus indicating that the practice was standard.

He claims that his superiors, Colin Myler, and News UK newspapers’ legal supremo Tom Crone withheld evidence from both the committee and News Corp’s top executives.

Thurlbeck’s claims are good for the Murdochs — Myler and Crone claim he was shown the email — but they ultimately put both of the latter in a corner they will have to fight their way out of. And what ammunition do they have?

No doubt there is no chance that Thurlbeck is angling for a bit of protection — he claims that there is “no chance” that Murdoch, pere or fils, would not have created an internal inquiry had they known of the shocking extent of hacking.

Well, maybe. It is quite possible that the Murdochs did not know that this practice — a legitimate journalistic tactic of last resort, and when directed at the powerful — had become the standard process of “news” gathering for the storyettes that NotW appended to its pics. But it beggars belief that close to £2 million in payouts were authorised to super-agents and the head of the Footballers Association/union without anyone high up asking to see the smoking pistol.

What’s next? Paul McMullan claims that he had kicked the whole inquiry back into touch by mounting his own surveillance operation on Brooks, the Murdochs, etc, and the whole Cotswalds gang (and seemed to direct some contempt at journos from “quality” papers, who were gaining all the credit for breaking the story).

The Murdochs should have expected that — if they didn’t, then they were victims of their own blinkered familial elitism. Doubtless that has now been punctured and they are wondering: what else is out there? What is on tape that they don’t know about? And what is out there that they do know of, and that is already shaping their activity?

One day you’re a great power, and the next the ocean is your mass grave. It’s an ill wind from heaven …