Former News International chief executive Rebekah Brooks said today that she was repeatedly told by the News of the World that allegations of phone hacking by the paper's journalists were untrue.
Appearing before the Commons Culture, Media and Sport Committee, she said it was only after she saw papers lodged in a civil damages case brought by actress Sienna Miller last year that she understood how serious the situation was.
"We had been told by people at News of the World at the time - they consistently denied any of these allegations in various internal investigations," she said.
"It was only when we saw the Sienna Miller documentation that we realised the severity of the situation."
Like Rupert and James Murdoch, Ms Brooks began her evidence by offering her "personal apology" for what had happened at the paper.
"Clearly, what happened at the News of the World and certainly (with) the allegations of voicemail intercepts of victims of crime is pretty horrific and abhorrent," she said.
Following her arrest on Sunday by police investigating the phone-hacking allegations, she said she was appearing with her lawyer, although she stressed she intended to be as open as possible.
"Since the Sienna Miller documents came into our possession at the end of December 2010, that was the first time the senior management of the company had seen some documentary evidence relating to a current employee," she said.
"I think we acted quickly and decisively then, when we had that information."
When asked whether she had been lied to by senior employees, Ms Brooks declined to answer because of the criminal investigation.
She said: "Unfortunately, because of the criminal procedure, I'm not sure that it's possible to infer guilt until those criminal procedures have taken place."
The former News International chief executive denied sacking Tom Crone, who was legal manager for the media giant.
She said he had spent "99%" of his time at the News of the World, and when the paper was closed he left the company.
The Sunday tabloid used private detectives like many other newspapers, she told the committee, and it had come around fourth in a chart of newspapers ranked by how often they used such services.
She said: "The use of private detectives in the late Nineties and 2000 was the practice of Fleet Street and after Operation Motorman and What Price Privacy?, Fleet Street actually reviewed this practice and in the main the use of private detectives was stopped."
Ms Brooks said she was "aware" of the use of private detectives during her editorship of the NOTW, but would not have approved specific payments.
Labour MP Tom Watson pressed Mrs Brooks on the use of private detectives by the News of the World.
"I was aware that the News of the World used private detectives, as every paper in Fleet Street did," she said.
"The payments of private detectives would have gone through the managing editor's office."
Ms Brooks denied she had met Glenn Mulcaire, who was convicted for phone hacking.
"I didn't know particularly that Glenn Mulcaire was one of the detectives that was used by the News of the World," she said.
"In fact, I first heard Glenn Mulcaire's name in 2006."
She said she believed Mulcaire was on the NOTW staff in the late 1990s and continued through to 2006 when he was arrested.
She was asked about her links with private investigator Jonathan Rees, a convicted criminal.
"I heard a lot recently about Jonathan Rees," she said. "I watched the Panorama programme, as we all did.
"He wasn't a name familiar with me, I am told that he rejoined the News of the World in 2005, 2006, and he worked for the News of the World and many other newspapers in the late 1990s."
Asked whether she found it "peculiar" that Rees had been rehired after serving a sentence for a very serious offence, she replied: "It does seem extraordinary."
Ms Brooks was pressed to name other private detectives who had worked with the News of the World.
"It isn't that I can't remember, it's that you have the same information that I have, which is from Operation Motorman," she told Mr Watson.
Asked whether she had any regrets, she said: "Of course I have regrets.
"The idea that Milly Dowler's phone was accessed by someone being paid by the News of the World, or even worse authorised by someone at the News of the World, is as abhorrent to me as it is to everyone in this room.
"And it is an ultimate regret that the speed in which we have tried to find out the bottom of these investigations has been too slow."
Ms Brooks said: "I think in the main, my use of private investigators while I was editor of the News of the World was purely legitimate and in pursuit in the main, as you know, for the addresses and whereabouts of convicted paedophiles through Sarah's Law.
"And that is my majority use, if not almost exclusive use, of private investigators myself."
Referring to her comments in 2003 that payments had been made to the police in the past, she said she was referring to a "wide-held belief" that payments had been made in the past, and not to a "widespread practice".
Ms Brooks said: "I can say that I have never paid a policeman myself. I have never sanctioned, knowingly sanctioned a payment to a police officer."
She added: "In my experience of dealing with the police, the information they give to newspapers comes free of charge."
Admitting that "things went badly wrong" at the News of the World, she would not comment on whether claims made by the Daily Mail that it has never published a story that was produced by hacking or blagging were credible.
Ms Brooks said: "You will have seen that, out of all the media groups in this country, that News International has been the one to openly welcome the Prime Minister's public inquiry into, I think, all Fleet Street practices."
She also welcomed the idea that journalistic standards should come under scrutiny.
"It is properly right that the code of conduct of journalists and the ethics of journalists are in constant review, because if they're not, it is the freedoms that this press enjoys which I believe in very strongly, that if there is not a constant view of conduct and ethics, then they are at risk."
Ms Brooks, who was editor of the News of the World at the time of Milly Dowler's disappearance in 2002, said that at the time she believed that the press had acted with "huge caution" and done its best to respect the family's privacy.
"In the light of what we believe the allegations are now, it may sound quite frankly ridiculous but at the time I believed that both on the Milly Dowler case, and in the Soham cases, the press had exercised huge caution and tried to respect the privacy of the families," she said.
"For example, I remember in Soham that one member of the Press Association was sent to go to the village and ... Fleet Street had come together and used the Press Complaints Commission code and adhered to it to respect the privacy of the families.
"Clearly these allegations that came out two weeks ago, if true, are appalling and obviously contradict that statement I made."
She said that she only learned of the allegations that Milly Dowler's phone had been hacked when it was reported in the press earlier this month.
She said she found it "staggering to believe" that anyone at the News of the World could have authorised it.
"My instant reaction, like everybody else, was one of shock and disgust that a family who had suffered so much already, that these allegations clearly added immeasurably to their suffering," she said.
"The first thing I did was write to Mr and Mrs Dowler with a full a apology to say that we would get to the bottom of the allegations."
Ms Brooks said: "I don't know anyone in their right mind who would authorise, no, sanction, approval, anyone listening to the voicemails of Milly Dowler in those circumstances.
"I just don't know anyone who would think it was the right and proper thing to do at this time or at any time.
"I know we know a lot more now but that's all I can tell you."
Asked whether she took personal responsibility for what happened, she replied: "I would take responsibility, absolutely, and I really do want to understand what happened, I think all of us do.
"Because that, you know, out of everything I've heard on this case, that was probably the most shocking thing I've heard for a long time and certainly the most shocking thing I'd heard about potential journalists who work for News International."
Ms Brooks said the decision to close down the News of the World was taken because it had lost the trust of its readers.
"Once that trust was broken, we felt that that was the right decision. Of course, it wasn't the right decision for the hundreds of journalists who worked on there, had done nothing wrong, were in no way responsible," she said.
"Every single one of them will be offered a job."
Ms Brooks said she believed Glenn Mulcaire's court testimony that he had not hacked phones before 2004.
"For all of us then, that was the reality. We were told in the trial in 2007, Glenn Mulcaire's pre-disclosure before sentencing stated categorically that he didn't start accessing voicemails until 2004. That's what he said, that's what he told the trial.
"It wasn't a myth, it was what everyone believed that the time."
But Labour MP Paul Farrelly questioned why the committee was "still being asked to believe that you as a hands-on editor and Andy Coulson simply didn't know what the news desk was up to".
Ms Brooks said: "I can't comment on what others knew and when they knew it and how they knew it. I can only tell this committee what I knew while I was editor of the News of the World and subsequently editor of the Sun, and as the chief executive I can account for my actions in trying to get to the bottom of this story."
She said she was "ringfenced" out of any investigation into phone hacking after reporting to News International that her own voicemail had been accessed.
The company has insisted that the then News of the World editor was on holiday when the phone of murdered schoolgirl Milly Dowler was hacked.
She replied: "It's slightly irrelevant where I was. I was the editor at the time. If this happened, then it's appalling, I didn't know it was happening."
Ms Brooks said the Milly Dowler story ran nine years ago.
"I'm told now that the story you're referring to was a single column on page nine of the newspaper of that edition," she said.
"I am sure questions were asked about where that information came from - they will have been asked of the reporter or they will have been asked by the news editor, the night editor would have checked them, the lawyer would have checked them.
"And there would have been a process around every story, whether it's a single column or a front page."
She added: "I can tell you now that it would not have been the case that someone said 'Oh yes, that came from an illegal voicemail interception'.
"It seems now that it was inconceivable that people didn't know this was the case but at the time it wasn't a practice that was condemned or sanctioned at the News of the World under my editorship."
Ms Brooks insisted that journalism was based on trust.
"If you think about the way a story gets published, of course it's on trust," she said.
"So you rely on the people that work for you to behave in a proper manner and you rely on the clarity of information that you are given at the time."
Asked whether she had any regrets over headlines now she had experienced the media "spotlight" herself, she said: "I don't think you'd find any editor in Fleet Street that didn't feel that some headlines that they've had published, they've made some mistakes.
"And I'm no different from that. There have been mistakes.
"On the other hand, despite being in the spotlight recently and having read lots of criticism that's justified and lots of criticism that was totally spurious, I would defend the right of the free press through my entire career, I think it is vital to us.
"And yes, it hasn't been particularly pleasant. It was one of the main reasons that I wanted to leave because I felt I was detracting from the amazing journalists and media executives and all the people that work in News International. I felt I was detracting from their incredibly good work."
Britain has a "robust and diverse press covering all spectrums and opinions" and its freedom should be "ensured for ever more", she added.
Ms Brooks said journalists and police officers had a "symbiotic relationship of exchanging information for public interest".
She was asked how often she had met David Cameron and his predecessors Gordon Brown and Tony Blair.
On Mr Cameron, she said: "I read the other day that we'd met 26 times ... I'm sure it is correct if that is what the Prime Minister's office say.
"The fact is, I've never been to Downing Street while David Cameron has been Prime Minister, yet under prime minister Gordon Brown and prime minister Tony Blair I did regularly go to Downing Street."
She said she has seen both Mr Blair and Mr Brown around six times a year.
Ms Brooks said she did not remember calling editors, including Daily Mail editor Paul Dacre in 2009, to talk about coverage of the phone-hacking story.
She said she would discuss "industry matters" with Mr Dacre on occasion.
The former tabloid editor also denied telling London mayor Boris Johnson that she wanted Guardian editor Alan Rusbridger "to go down on his knees" and beg her forgiveness.
Ms Brooks said that many of the claims made about her relationship with Mr Cameron - who, like her, has a home in Oxfordshire - were untrue.
"I have never been horse-riding with the Prime Minister, I don't know where that story came from," she said.
"There is a lot out there that just isn't true, particularly around this subject of my relationship with David Cameron.
"The truth is that he is a neighbour and a friend, but I deem the relationship to be wholly appropriate and at no time have I ever had any conversation with the Prime Minister that you in the room would disapprove of."
She also dismissed suggestions that she had advised Mr Cameron to make Mr Coulson his director of communications after he left the News of the World in 2007.
"I think it is a matter of public knowledge that it was George Osborne, the Chancellor's idea, that when Andy Coulson left the News of the World they should start discussions with him on whether he (should) be the appropriate person to go into Tory HQ," she said.