LONDON (AFP) - Former Murdoch executive Rebekah Brooks on Thursday denied knowing anything about phone hacking while editing Britain's News of the World tabloid, as she took the stand for the first time in her trial.

Brooks is charged with conspiring in voicemail hacking, conspiring to bribe public officials and two counts of trying to cover up her alleged crimes, although she was cleared Thursday of a fifth charge of approving a payment for a photo of Prince William in a bikini.

Almost three years after she was first arrested in July 2011 and three and a half months into the trial, the former chief executive of Rupert Murdoch's British newspaper stable News International finally had a chance to put her side of the story.

Brooks was asked by her lawyer if she had ever heard mentioned the name of Glenn Mulcaire, a private detective who worked for the tabloid while she was editor and who was jailed in 2007 for hacking phones.

Seated in the witness box at England's Old Bailey central criminal court in London, wearing a blue dress and white cardigan, her red curly hair pinned back, she replied: "No".

When asked if hacking had ever been brought to her attention, Brooks replied: "No, not at all." The 45-year-old acknowledged that private detectives were used at the News of the World but said it was "common practice" in the British newspaper industry.

Brooks edited the weekly Murdoch tabloid from 2000 to 2003 before becoming editor of The Sun, its daily sister title. In 2009 she was promoted to News International chief executive.

She resigned in July 2011, a few days after Murdoch shut down the News of the World over the hacking scandal and a few days before she was arrested.

Before Brooks began giving evidence, the judge ordered the jury to find her not guilty on one of the five charges against her - one of conspiring to commit misconduct in public office.

Brooks was accused of sanctioning a payment of £4,000 (S$8,400) to a public official for a picture of Prince William dressed as a bikini-clad Bond girl at a party at Sandhurst, the British army's elite officer training school.

The image was never published but led to a story in The Sun in September 2006 with the headline "Willy in a Bikini" together with a mocked-up picture of the second-in-line to the throne wearing a green swimsuit.

In her testimony, Brooks talked about some of her greatest scoops, including an interview with Divine Brown, the Hollywood prostitute caught having sex with British actor Hugh Grant in 1995.

The story cost the News of the World £250,000, she said, adding: "It was probably one of the biggest expenses that I had ever dealt with." She also said: "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 have heard that the News of the World investigations unit was called the "dark arts department", alluding to alleged illegal activity. "I don't recognise that description," she said.

Brooks, her husband and Carter are among seven defendants in the trial, including Andy Coulson, her successor as News of the World editor and one-time lover. All the defendants deny all the charges against them.

The case, expected to last into May, resumes Friday.