Media playback is unsupported on your device Media caption Rebekah Brooks has been cleared of one charge in the phone-hacking trial

Rebekah Brooks has said she never heard of a private investigator who has since been jailed for phone hacking while she was editor of the News of the World.

Mrs Brooks said that during her leadership of the paper, she never heard investigator Glenn Mulcaire's name mentioned.

Earlier, she was formally cleared of one count of conspiracy to commit misconduct in public office.

Mrs Brooks, one of seven defendants on trial, denies four other charges.

On her first day of giving evidence at the phone-hacking trial at the Old Bailey, she was asked if Mulcaire's involvement in accessing voicemail messages was ever brought to her attention between May 2000 and January 2003.

She replied: "No, not at all."

Asked by her barrister Jonathan Laidlaw QC if she had heard Mulcaire's name mentioned during that time, Mrs Brooks said: "No."

Mrs Brooks told the court there were private detectives working at News of the World, and added that it was "common practice in Fleet Street".

Mulcaire was jailed in 2007, along with the News of the World's then-royal editor Clive Goodman, after admitting intercepting voicemails.

Image copyright PA Image caption Rebekah Brooks left the Old Bailey with husband Charlie

Mrs Brooks denied the News of the World's investigations unit was the "dark arts department" and was involved with alleged illegal activity.

She added: "The investigations unit, I think, did some great stuff while I was there. I don't recognise that description."

Asked by her barrister if the unit, which came to an end in 2001, had been set up specifically to hack phones, she replied: "It's just not correct."

Mrs Brooks said she would not have known where every story in the newspaper had come from.

"It's impossible for an editor to know every source for every story," she told the court. "Of course it's impossible, with the sheer volume that's coming in to the paper."

The jury heard details of major stories Mrs Brooks had worked on.

She said while she was features editor at the News of the World in 1995, she had agreed a $100,000 (£60,000 at current exchange rates) deal with prostitute Divine Brown after actor Hugh Grant was caught with her.

But she said the newspaper ended up spending far more - about $250,000 (£150,000 at current exchange rates) in total - flying Ms Brown and her family to "the desert", possibly Nevada, to keep her away from rival newspapers.

Rivalry 'ingrained'

At the time her weekly spending limit was supposed to be £50,000 to £60,000.

"It was probably one of the biggest expenses that I had ever dealt with," she said.

Mrs Brooks said there was fierce competition between the news and features departments at the News of the World, as well as with other News International papers.

There was "probably a bit of old-school misogyny" towards her, she said, but competition between the two desks was "ingrained into the News of the World's history".

Despite being in the same building, each publication was accessed by swipe card.

When a route to a News of the World canteen was planned that went past the offices of The Sun, the daily newspaper had its windows frosted, she said.

At the beginning of her evidence Mrs Brooks spoke about her career in journalism.

In April 1989, she got a job as a features researcher at the News of the World's Sunday magazine, before being promoted to feature writer in September that year, she said.

Image copyright PA Image caption Rebekah Brooks said she first met Tony Blair in 1996

Mrs Brooks told the court she moved to the News of the World's features department in 1992, and became features editor in 1994.

She said that, at the time, the features department was known as the "pink parlour" because there were more women than men working there.

Although the News of the World had a female editor then, the newsroom was male dominated, added Mrs Brooks.

In 1995, she became acting deputy editor of the News of the World at the age of 27.

Prince picture

On Wednesday the court saw an email from Mrs Brooks in which she claimed former Prime Minister Tony Blair had offered to be an "unofficial adviser" to senior News International figures when the hacking story broke.

Mrs Brooks said she met Mr Blair, along with the rest of the "original New Labour crew", in 1996. The Sun and the News of the World switched to support Mr Blair in 1997.

Who are the defendants? Image copyright Various agencies Read profiles of the defendants

Mr Justice Saunders earlier directed the jury to acquit her of a charge of conspiracy to commit misconduct in public office, saying there was "no case to answer".

In that count, Mrs Brooks was accused of authorising a Sun reporter to pay a serving member of the armed forces £4,000 for a picture of Prince William dressed in a bikini at a fancy dress party at the Royal Military Academy Sandhurst.

Mrs Brooks, 45, still faces two charges of conspiracy to pervert the course of justice, one of conspiracy to commit misconduct in public office and one of conspiracy to hack voicemail messages - all of which she denies.

All seven defendants deny the various charges against them.