The cruel arrest and failed prosecution of former detective chief superintendent Dave Cook shows the extent to which those in power will go to ensure that Britain has secret police.
And it underlines again how News Corp allowed its Management and Standards Committee, set up at the height of the hacking scandal in 2011, to betray its own journalists and their confidential sources.
Cook was cleared by the Independent Police Complaints Commission yesterday nearly four years after his arrest in a dawn raid back in January 2012 on suspicion of misconduct in a public office.
His crime had been to share information relating to a notorious unsolved murder, which had been mired in allegations of police corruption, with a News International journalist.
Even though there was no suggestion of money changing hands, and this was clearly a serious matter of public interest, my understanding is that News Corp's MSC passed on information about Cook to the Met's Operation Elveden.
At the time, lawyers in New York were seeking to "drain the swamp" as they put it, seeking out any further evidence of criminality at News Corp's UK subsidiary News International (now called News UK). The News of the World had just closed and the company wanted to ensure its surviving newspaper titles were safe: The Sun, Times and Sunday Times.
The IPCC said yesterday that Cook was targeted over the unauthorised disclosure of secret files to a journalist.
But my understanding is this does not tell the whole story.
Cook was investigating the notorious unsolved murder of Daniel Morgan, a private detective killed with an axe in South London in 1987, at the time the disclosures were made (from 2006 onwards).
Part of his job in leading the new investigation would have been to plant stories in the press in order to help gather evidence and encourage new witnesses to come forward.
The Morgan murder has been the subject of five failed police inquiries and is now being investigated by an Independent Panel set up along the some lines as the Hillsborough inquiry.
It is looking, among other things, at the role played by police corruption in protecting those responsible for the murder from being brought to justice and the failure to confront that corruption.
One does not have to be a conspiracy theorist to suspect that throwing the full weight of the law against an officer who made disclosures to a journalist about the Met's failure to catch Morgan's killer stinks.
Morgan's family believe Daniel was killed because he was set to make revelations about police corruption.
Nearly four years after Cook's arrest, the Crown Prosecution Service said it would not be in the public interest to prosecute him. But why was Cook prosecuted in the first place and why has his ordeal been allowed to drag on for so long?
Again, one does not have to be a conspiracy theorist to suspect that the motive was to silence him and others who might be tempted to follow his example.
Around 30 public officials who were paid for stories by The Sun and News of the World have been convicted as a result of News Corp's decision to share information with Operation Elveden.
Others have lost their jobs over disclosures to journalists in which no money changed hands.
Ealing borough police commander chief superintendent Andy Rowell was arrested in a 6am raid on his Wiltshire home in February 2013 as a result of information given to the Met by News Corp's MSC.
Rowell shared information with a journalist about the arrest of a high-profile footballer for rape. He was sacked for gross misconduct in January this year.
Detective chief inspector April Casburn called the News of the World on 11 September 2010 to raise concerns about the fact anti-terrorism police resources were being devoted to investigating phone-hacking. She was paid no money, and no story appeared. But because the reporter who took the call said he believed she wanted payment for the information she was jailed for 15 months.
Again she was prosecuted as a result of information shared with the police by News Corp's MSC.
Today UK police officers are, not surprisingly, deeply reluctant to have unauthorised contact with journalists lest they go the same way as Dave Cook.
The result is that the public are less safe. This is because the police are less transparent, so more vulnerable to the corruption which secrecy and cover-ups can breed. And because the free flow of information between journalists and police officers helps solve and prevent crime.
Police forces need to stop arresting and intimidating officers in cases of contact with the media where no money has changed hands and no harm has been done.
And News Corp needs to publicly reaffirm its belief in the protection of confidential sources and reveal what steps have been taken to ensure the disastrous actions of its New York-based Management and Standards Committee are never repeated again.