When he appeared before MPs last July to face questions over phone hacking, Rupert Murdoch described it as "the most humble day of my life". It would be interesting to know how the veteran media tycoon regarded 19 April 2012. By even his standards, yesterday was grim.

The Labour MP Tom Watson and The Independent journalist Martin Hickman called a press conference to disclose the contents of the book they have co-authored, Dial M for Murdoch. Among the revelations was how Murdoch's News International targeted members of the Commons select committee who were investigating it. Reporters were ordered to find out everything they could about every member: who was gay, who had affairs, anything they could use. "Each reporter was given two members and there were six reporters."

The graphic picture the book paints is of a state within a state, of a company that spun its web of influence throughout the British media, politics, police and public life. But make no mistake: that hegemony is crushed. Indeed, the authors showed that by publishing their work.

To emphasise the collapse, there were more arrests yesterday in the police inquiries now under way, among them The Sun's royal editor on suspicion of conspiracy to corrupt and conspiracy to cause misconduct in a public office.

Then came the announcement from solicitor Mark Lewis that he would be launching proceedings in the US, in Murdoch's backyard, on behalf of people whose phones were hacked there. And the Leveson Inquiry said that James Murdoch would be giving evidence on Tuesday of next week, and that the following day-and-a-half had been set aside for the questioning of his father.

Any sense of Murdoch Snr exercising control over events has long since disappeared. Surely, MPs cannot let Dial M for Murdoch pass. They must launch another inquiry, this time into their attempted smearing.

On it goes. Next week, before Leveson, promises more of the same. If quizzing by MPs was humbling, what will a very public cross-examination before a senior judge be like? These are dark days for Rupert Murdoch – but brighter ones for a Britain shaking off his pervasive power.