Unmasked: the politicians who courted the media even as journalists plundered their private lives.
It's all in Hack Attack, Davies' book on his reporting of the phone-hacking scandal carried out for the quality left-leaning Guardian newspaper.
Next month, award-winning reporter Davies is in New Zealand for the Auckland Writers Festival where he'll talk about his book - which is being adapted into a movie directed by George Clooney - run a (sold-out) masterclass on investigative reporting and dissect the Weekend Herald on stage with editor Shayne Currie.
As a courteous English visitor, he'll undoubtedly be polite. Then again, he is the man often credited with killing off the News of the World.
Davies' journey into the dark heart of British journalism began before Hack Attack. In 2008, he wrote Flat Earth News, a caustic analysis of the decline of an industry in which he had largely worked since 1976.
The book focused on the quality press, but talking to reporters from newsrooms across Fleet Street "about the stories behind stories" he heard tales of constant petty-criminal behaviour. It didn't fit with the theme of the book but Davies included the excesses of the red-top tabloid rabble, including bribery and phone message hacking.
That's where it might have stayed, were it not for the News of the World's managing editor Stuart Kuttner. In a radio duel with Davies, Kuttner insisted there was the case of a single "rogue reporter" - fired and jailed. The editor on whose watch this had happened, Andy Coulson, denied knowledge and resigned.
When Davies left the studio, he took a call telling him of widespread phone hacking at the News of the World, by journalists and by private investigators hired to work for the paper. That was the thread. Davies pulled at the thread and the first story, alleging widespread hacking and a cash settlement with a victim, ran about 17 months later.
It mattered, says Davies, because Coulson had become press secretary to David Cameron. If Cameron won the 2010 elections - as expected - he would become Prime Minister and Coulson would have huge power.
To Davies, it seemed very difficult for Coulson to have been ignorant of widespread hacking. "If he's lying about what went on, he's in exactly the wrong job. He's responsible for the next Prime Minister's communication with the country and you really don't want a liar in that position."
The Coulson factor spurred Davies on, as did the style of reporting practised by the News of the World: finding targets, then "monstering" people with abusive, intrusive coverage. Of the phone hacking, he says: "It's actually quite low-level crime. But if you combine it with the cruelty, then it's just wrong. Somebody has got to stop them."
And so he did. Bit by bit, story by story, the defences of ignorance collapsed.
Davies became an active protagonist, outlining in the book how he met with Formula 1 boss Max Mosley, who had been shamed by the News of the World. Mosley told Davies he was willing to put his fortune to work targeting the paper. Davies became a conduit between new victims and Mosley, whose money would pay for lawyers for those who wanted to sue News International.
It was necessity which made him a conduit, says Davies. The need was to have the legal cases draw into court the documentation which would drive the stories.
"Very early on I think we understood what exactly the picture was with the hacking. But unless we can get paperwork that proves it, these powerful organisations are going to carry on lying and the truth won't be told. By steering people into the channel to start suing to get to court I could eventually get the power of a judge onside, ordering disclosure of documents.
"If you want to expose abuse of power, you will be starting a fight and so you have to fight to defend your patch and uncover the truth."
Davies is scathing of the illegal techniques and the results they produced. "It's kind of like going fishing by dropping dynamite in the water ... saying 'I've caught some fish'. It ain't reporting."
Resisting the tide was media mogul Rupert Murdoch and Rebekah Brooks, his former superstar editor of the Sun and News of the World. She had been recently appointed by Murdoch as chief executive of News International in the UK.
As Davies writes in Hack Attack, the company was divided over handling of the scandal while Brooks maintained her close relationship with Murdoch. "She was constantly reassuring him and perhaps ended up believing it herself."
"She's in the habit of winning. She just doesn't have a history of failing to wriggle out of the problems in front of her. She just assumed it would all be all right. She's then feeding that message through to Rupert very directly and he's getting the wrong picture and therefore making bad decisions."
By 2011, News International prepared to contain the scandal with concessions and damages payments to victims including actress Sienna Miller and former Cabinet minister Tessa Jowell. In its London office, Davies says "they were fighting like rats in a sack". While Brooks failed to act, other executives were charting worst-case scenarios. One whiteboard carried the assessment: "It's manageable as long as it doesn't go Main Street".
Which is exactly where it went.
First it was the revelation News of the World journalists hacked the phone of murdered teenager Milly Dowler. Then it emerged others - families of slain soldiers, other dead teenagers, victims of terrorism - had become targets for the paper's illegal actions, fodder for the relentless appetites of the News of the World.
The outrages had been cultured in the aggressive, bullying and unpleasant newsrooms of tabloid newspapers. Coming back without the story was not an option, so reporters - sometimes good people doing bad things - pushed and broke through boundaries.
It was the tipping point. The News of the World was closed, what Davies calls a defensive position by News International. Politicians who once worked to befriend Murdoch and his editors now publicly decried the paper's behaviour. A public inquiry was launched into the phone hacking scandal and, more broadly, the ethics of the British press, with a senior judge appointed to run it.
Parliamentary inquiries were made. The press regulator, which had mounted a series of odd defences, looked foolish and inadequate. The police, after years of avoiding difficult questions about its lacklustre inquiries and lack of straight answers, were finally beginning to investigate properly.
And the numbers of victims continued to mount.
Arrests were made. Brooks was found not guilty, her former lover Coulson was jailed. A range of others have since been convicted in the courts. Senior police resigned. Reputations were ruined. Murdoch's companies paid hundreds of millions of pounds in legal fees and settlements.
"At the tabloid end, the crime was very widespread. I don't think there was any tabloid newspaper that wasn't breaking the law. People are moving from one newspaper to the other and taking their contacts and taking their techniques with them," says Davies.
"At the tabloid end, it's fair to say everybody knew what was going on because an awful lot of them were at it."
