News of the World scandal: Sienna Miller's tale

For years, News International had managed to fend off repeated allegations that there was a culture of phone hacking at the newspaper by insisting the problem was confined to private investigator Glenn Mulcaire and "rogue reporter" Clive Goodman, both of whom had been jailed for their actions.

The Murdochs' insistence that senior executives at the paper had no knowledge of what was going on was lent credibility by both the police and Press Complaints Commission (PCC) inquiries, which gave the newspaper a relatively clean bill of health.

But documents lodged with the High Court by Miller and her legal team last December suggested senior executives, including former news editor Ian Edmondson and chief reporter Neville Thurlbeck, were not only aware that phone hacking was going on, but were party to the transcripts, a revelation that blew the rogue reporter theory out of the water. "It was only when we saw the Sienna Miller documentation that we realised the severity of the situation," Brooks said.

In a further twist, it is now being claimed that, contrary to what James Murdoch told the inquiry, a "smoking gun" email - the same email on which the Miller case hung - had in fact been brought to his attention two and a half years earlier. Former editor Colin Myler and legal manager Tom Crone say it was passed to him when the News of the World was examining a lawsuit from Professional Football Association chief executive Gordon Taylor, a case which was later settled out of court to the estimated tune of 700,000.

The incendiary claim - denied by Murdoch - that he misled the select committee, has been passed to Scotland Yard. It will examine whether or not the News Corp executive broke the law by failing to pass on evidence of criminality, an act which, combined with an alleged attempt to "buy" Taylor's silence, could constitute conspiracy to pervert the course of justice.

Whether Murdoch knew of the email's existence or not, it is clear the Miller case represented a turning point. With the actress unwilling to accept the "hush money" paid to other public figures and the incriminating documents set to enter the public domain, it was clear the game was up.

Within days, Edmondson had been fired and evidence implicating him and Thurlbeck had been handed to Scotland Yard, prompting a new, and far more thorough, police investigation. With The Guardian pursuing a relentless campaign against the News Of The World and the culture, media and sports select committee ramping up the pressure, revelations that murder victim Milly Dowler also had her emails hacked into, lit the touchpaper of public outrage.

Ironically, much of the evidence Miller's legal team uncovered was not new. Most of it was contained in Mulcaire's notes which were handed over to the first police investigation into hacking in 2006.

So how did a celebrity - who'd provided many a red-top exclusive in her time - succeed in exposing the extent of the phone hacking scandal where the police, the legal firm Harbottle and Lewis (brought in by News International to examine internal emails) and the PCC had failed?

Is it simply a coincidence that the woman who once doused a journalist with urine was the one to start the dominoes toppling? Or did the actress's visceral hatred for the newspapers which had breached her privacy - and the fact she was not a member of the infamous Chipping Norton set - simply give her the determination and neutrality to cut through the web of misinformation which allowed the phone-hacking scandal to lie dormant for so long?

There are some who would say Miller is the last person who should be lecturing News International on ethics and morality. The reason she proved such a target for the tabloids was, after all, her tumultuous love life: her affairs with Jude Law and then Balthazar Getty brought her a reputation as a home-wrecker (although Law had recently divorced Sadie Frost when the two first met).

Throughout her early career she was hounded by photographers who staked out her homes, pursued her in cars and on motorbikes and even stalked her while she walked her dogs in the park.

Unlike many celebrities, however, Miller refused to accept such intrusion as part and parcel of the fame game. Long before Hugh Grant jumped on the bandwagon, she was campaigning for her right to privacy, taking on the paparazzi both through direct action (she also once hit a photographer with a handbag) and through the courts.

In 2008, she won separate cases against a photographer who took shots of her naked in a closed film studio in Surrey, the photo agency which employed him and The Sun and the News of the World which printed the images.

Months later, she won a further victory against another agency - Big Pictures - in a landmark action under anti-harassment laws designed to tackle animal rights protesters. In court, her lawyer Mark Thomson produced 23 images showing her in distress after having been "chased, harassed or shouted at" and said she'd been hounded by groups of 15 photographers some of whom mounted 24/7 surveillance on her. Not only did the agency agree to pay her 53,000 damages plus costs, it undertook not to photograph her at her home or pursue her for pictures in the future.

The story that led to the voicemail lawsuit involved revelations about cracks in her relationship with Law and appeared in 2005, long before her privacy cases. But the first police investigation into phone hacking - prompted by a story about an appointment Prince William had made with a knee surgeon - had focused on claims the mobile phones of royal aides were being intercepted. Although it was revealed some non-royal public figures, including Taylor and Max Clifford also had their phones hacked, the finger of blame was pointed at Mulcaire and Goodman alone.

Harbottle and Lewis - brought in after Goodman went to an industrial tribunal on the grounds that phone hacking was widespread on the newspaper - examined thousands of emails passed to them by News International and there was no evidence to suggest anyone else was involved in any way.

It wasn't until The Guardian printed a story claiming 3,000 celebrities may have had their phones hacked that it became clear the practice was widespread.

It also revealed that the News of the World had made payments in excess of 1 million to three people subject to phone hacking, including Taylor. The payment to Taylor - it later emerged - had been signed off in June 2008 by the directors of News Group Newspapers, suggesting awareness of the matter at the highest level.

Brought in to "re-examine" the evidence in the wake of The Guardian stories, assistant commissioner of the Met John Yates spent just eight hours reviewing existing evidence before deciding the original investigation had been sufficient. A re-examination of the affair by the PCC led members to conclude they had not been misled "in any material way".

By now, however, dozens of public figures, including Miller, were taking matters into their own hands. Through their lawyers, they managed to get hold of Mulcaire's notes, which had been passed to the Met, but never fully investigated. It was here they found the so-called "smoking gun" email - a transcript of 35 voicemail recordings, marked "for Neville" - an apparent reference to Thurlbeck. Other emails made reference to Ian, said to be Edmondson.

Subsequently, a forensic computer specialist that the company hired to help it comply with a court order to turn over documents made another discovery - three emails sent to Edmondson containing PIN codes that could allow access to voicemail.

All this information would have been in the documents filed at the High Court last December, sounding the death knell for the Murdochs' "rogue reporter" claim.

After years of the affair trundling along, things started to gather pace. In February, the culture, media and sport select committee condemned the testimony of the News of the World witnesses at a 2009 hearing, referring to "collective amnesia" and "deliberate obfuscation".

Then in April, Miller won her case, and was awarded 100,000 in damages. That was far short of Taylor's settlement, but she got what she wanted, an admission of wrongdoing and a public apology.

In fact, she got much more. Before the case even came to court, Edmondson, Thurlbeck and reporter James Weatherup had been arrested and questioned. Later, News International issued a blanket apology, saying: "It is now apparent that our previous inquiries failed to uncover important evidence."

Further arrests - including those of Andy Coulson, Brooks and former executive editor Neil Wallis - followed revelations that Milly Dowler and the families of 7/7 victims had also had their voicemail messages intercepted.

Miller must have watched with astonishment, and not a little schadenfreude, as mounting public outrage led to the closure of the News of the World, the resignation of Brooks, Met commissioner Paul Stephenson and assistant commissioner Yates, and the announcement of a public inquiry.

With the Chipping Norton set in disarray and the scandal now snapping at the heels of both David Cameron and James Murdoch, it is difficult to see how much more comprehensively the establishment could have been upended.

Although it was not the sole factor, Miller's determination played a key part in blowing the affair open. "It was ultimately just about standing up for yourself, what you believe is right and wrong," Miller said of her battle against the tabloids, in an interview not long before the phone hacking case came to court. Buoyed by the victories they have achieved, many celebrities are continuing to pursue phone hacking claims against News International. Last week, Hugh Grant - now a staunch campaigner for privacy - and his former girlfriend Jemima Khan won a court order forcing the Met to hand over information relating to their phones being hacked.

In the US, the stakes are rising with the US justice department said to be preparing subpoenas in relation to FBI inquiries into allegations that 9/11 victims had their phones hacked into and that, by paying police officers for information, News Corp is guilty of violating the Foreign Corrupt Practices Act.

Closer to home, Myler and Crone's statement, claiming James Murdoch was "mistaken" about the "For Neville" email means he is likely to be recalled to the culture, media and sport committee to clarify his evidence.

If he were found to have deliberately misled parliament, it would raise fresh questions as to whether he is a "fit and proper" person to be chairman of BSkyB. Those who hate News Corp seem to be inching closer to getting what they really want: a Murdoch scalp.

For Miller, however, taking on the might of the Murdochs was less about bringing down the media mogul and more about securing a bit of peace for herself and her family.

"The evidence I had was so substantial it had to move forward," she said. "I definitely contemplated not doing it, because it's an incredibly powerful thing to take on, and to be a person on your own doing it - it's pretty scary. But I don't regret it. All the legal action I've taken against newspapers has had a massively positive effect on my life and achieved exactly what I wanted."