In the lexicon of journalism the word "unprecedented" has reached cliché status. But I make no apology for using it to describe both the allegation against the News of the World that it hacked into a murdered girl's voicemail messages and the public response to it.
Though the phone-hacking scandal has been running since 2006 and has grown in intensity in the past year, no incident has captured the public imagination like the revelation that the paper intercepted and deleted messages from the mobile phone of 13-year-old Milly Dowler after she went missing in March 2002.
Senior politicians were so shocked they seemed unable to find adequate phrases to describe their feelings. Prime Minister David Cameron called it "a truly dreadful act" and Labour's leader Ed Miliband thought it ''a stain on the character of British journalism''.
They were echoing a chorus of criticism in the media and on the internet. Social media sites, such as Facebook and Twitter, were dominated by the topic. Callers to radio phone-ins were united in their hostility to the paper's callous actions.
Several advertisers began to review whether to continue buying space in the paper. Ford jumped first by announcing that it is pulling its ads. Again, this is almost unprecedented - it has happened only once before to a national paper when the Daily Star published material in 1987 regarded as pornographic. It led to the editor being fired.
Recent legal settlements to News of the World hacking victims such as Sienna Miller and Andy Gray, of £100,000 and £20,000 respectively, had passed without much public comment. Rupert Murdoch's News International thought it had found a way to seal off the paper from further criticism by opening its deep purse.
But public apathy has been transformed into public rage. The fact that a private investigator acting on behalf of the News of the World had dared to intervene into a criminal investigation changed everything.
Yet greater ferocity followed the revelation that police have also contacted the parents of two 10-year-old girls, Holly Wells and Jessica Chapman, who were murdered in August 2002, to warn them that their phones may also have been hacked on behalf of the News of the World.
It suggests, as many of us have been saying for years, that hacking - which is, of course, an illegal act - took place as a matter of course at the behest of the Wapping newsroom. It was used to discover private information about anyone - actors, PR agents, secretaries, footballers, TV presenters and people caught up in murder investigations - deemed likely to provide sales-winning copy for the newspaper.
In other words, journalistic ethics were sacrificed on the altar of commerce. Clearly, by hiring private investigators to do the job, the journalists were trying to distance themselves from an illegal practice. That makes them just as culpable.
There is another worrying aspect to this whole affair, however: the role of the police. In 2006, the News of the World's royal editor, Clive Goodman, and the private investigator, Glenn Mulcaire, were arrested for intercepting voicemail messages on the phones of aides to the British royal family.
Police found hundreds of documents in Mulcaire's house with the names of other people who had been hacked. Yet they chose to inform very few of them and did not investigate any further. That failure has led to a new inquiry, known as Operation Weeting, by the Metropolitan Police.
There must be questions too about Surrey police for failing to pursue the News of the World over its interception of Milly Dowler's phone.
The only way to get to the bottom of this sordid business is to hold an independent public judicial inquiry, and MPs are likely to call for that in a Commons debate later today.
However, that public inquiry cannot happen until the police investigation has concluded. Meanwhile, the pressure on the woman who was editor of the News of the World at the time of the Milly Dowler incident, Rebekah Brooks, will surely get more intense in the coming days.
She is now chief executive of News International and regarded as Rupert Murdoch's closest ally. But can she resist the persistent calls from members of the public and politicians to resign?
If more advertisers follow Ford's lead, if readers do refuse to buy the paper, then she will be out.
Commerce was behind the hacking. Commerce will decide her fate.
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