Rebekah Brooks has denied any knowledge of phone hacking while she was editor of the News of the World, insisting it was impossible for her to know the source of every story that appeared in the tabloid.
As she took to the witness box for the first time at the Old Bailey today, the former News International (NI) chief executive said she had not heard private detective Glenn Mulcaire's name mentioned, nor anything about his hacking activities, during her leadership from May 2000 to January 2003.
Wearing a white cardigan over a royal blue dress, with her red hair pinned back, the 45-year-old appeared calm as she began her long-awaited defence over allegations of phone hacking and paying public officials.
After describing her rapid rise to the upper echelons of NI, Brooks was asked about her knowledge of Mulcaire - who has already admitted charges of phone hacking - and his activities.
Asked by her lawyer Jonathan Laidlaw QC: " Had you heard of Mr Mulcaire's name?", she replied, "no".
The barrister asked: " Had anybody as far as you can remember spoken his name in your presence?".
Again she answered "no".
Mr Laidlaw went on: "P hone hacking? Accessing voicemail messages? Was any involvement he had in that practice ever drawn to your attention?"
In the tense exchange, Brooks answered: " No, not at all."
Brooks told the court that around 200 stories made it into the newspaper out of a pool of stories twice the size.
"You would always have access to the wires, the Press Association. You would also have the news on so you were getting stories from all sorts of places," she said.
She added: "It's impossible for an editor to know every source for every story. Of course it's impossible with the sheer volume that's coming into the paper."
Jurors heard that an investigations unit set up by Brooks was dubbed the "dark arts department", alluding to alleged illegal activity.
The unit was run by former news editor Greg Miskiw - who Brooks today described as having an "air of mystery" - who has pleaded guilty to conspiracy to hack phones by tasking Mulcaire with targets.
Asked about suggestions that the unit had been set up specifically to hack phones, Brooks said: "It's just not correct."
The unit came to an end in 2001 after it became apparent that it "wasn't working", the court heard.
During Brooks' evidence, she described meeting former prime minister Tony Blair and the ''original New Labour crew'' before the Sun famously switched political allegiance.
Her then boyfriend EastEnder Ross Kemp, a card-carrying Labour supporter, had been asked to open a rally for then shadow education secretary Mr Blair, whose mantra at the time was Education, Education, Education, she said.
'' I went with him and that's when I met the New Labour team - Tony Blair and his wife Cherie, Alastair Campbell and his wife Fiona Millar and Peter Mandelson - the original New Labour crew. "
Describing The Sun and News of the World's switch to support Mr Blair in 1997, she said: ''The Sun had supported the Tories for a long time and they supported Tony Blair in favour of John Major very early on. It was a big thing.''
Yesterday, the trial heard how Brooks's relationship with Mr Blair continued at the height of the hacking crisis in July 2011.
Reporting an hour-long phone call with Mr Blair to James Murdoch, Brooks said he told her to ''tough up'' and offered to be an unofficial adviser.
Brooks, 45, is accused of conspiring to hack phones, conspiring to commit misconduct in public office and conspiring to pervert the course of justice in a bid to cover it up.
Earlier, the jury was instructed to formally acquit Brooks on a charge of conspiracy to commit misconduct in a public office, over an alleged conspiracy to pay public officials for a picture of Prince William in a bikini, after judge Mr Justice Saunders ruled there was no case to answer.
Brooks is accused of conspiring to hack phones alongside one-time lover Andy Coulson, who served as her deputy editor on the NotW and went on to become editor, as well as f ormer managing editor of the News of the World Stuart Kuttner.
She described Kuttner as having an " incredibly good reputation" today, but added "I wouldn't say we were ever friends; he was a different generation and a different world almost."
Brooks said she did not socialise with Miskiw and NotW former chief reporter Neville Thurlbeck, who has also admitted conspiring to hack phones.
Describing her dealings with media mogul R upert Murdoch, she said he would always call on a Saturday night, before the newspaper was published the following day.
Recalling the first time he came to her office, she said: ''I remember him coming into my office for the first time when I was deputy editor and he sat down and said 'It's a big challenge at a young age', kind advice.
"'You've got a long career ahead, take your time, learn on the job'.
''He was particularly keen for me to take a very strict path in any kind of publicity.
''He wasn't very fond of editors ... going on Radio Four and spouting forth about their opinions, he didn't like that.''
She added: ''I made the fatal error of telling him Woman's Own wanted to interview me, and his reaction was very grim.''
Brooks, 45; Coulson, 46; former NotW royal editor Clive Goodman, 56; Brooks's former personal assistant Cheryl Carter, 49, Brooks's racehorse trainer husband Charles Brooks, 50, head of security at News International Mark Hanna, 50, and ex-NotW managing editor Stuart Kuttner, 73, deny all charges.
The case was adjourned until tomorrow.