The prime minister's director of communications has denied printing lies and being a bully while giving evidence at the Tommy Sheridan perjury trial.
Former News of the World editor, Andy Coulson, also said he believed a tape - which allegedly shows Mr Sheridan admit to visiting a sex club - was genuine.
Mr Sheridan and his wife Gail, both 46, deny charges of perjury.
They are accused of lying during his successful defamation case against the News of the World in 2006.
The former Scottish Socialist Party (SSP) leader won £200,000 when he took the newspaper to court after it printed allegations that he had committed adultery and visited a swingers' club.
The Sheridans were charged with perjury following a police investigation.
Mr Coulson, who is Prime Minister David Cameron's director of communications, was editor of the News of the World between 2003 and 2007.
At the High Court in Glasgow, he was questioned by Mr Sheridan, who is conducting his own defence.
The former journalist told the court that he had viewed a video tape - which his newspaper had paid £200,000 for - that is alleged to show Mr Sheridan admitting to visiting a swingers club.
Mr Coulson said he travelled to Glasgow, viewed the tape and suggested to the Scottish editor, Bob Bird, that he should do what he could to verify its authenticity.
He told the court he believed the tape to be authentic on first viewing.
When asked by Mr Sheridan why he thought this Mr Coulson said: "It was you."
Mr Sheridan asked Mr Coulson if he had seen his face on the tape. Mr Coulson said no but he was familiar with his voice.
Asked if that was because he had heard his voice through recordings from private investigators, Mr Coulson said he certainly did not remember doing so.
Mr Coulson also told the court that no one was more sorry than he was when a member of staff at the News of the World was arrested for hacking mobile phones belonging to members of the Royal household.
Earlier, the trial heard from former SSP member and ex drama teacher, Pat Smith.
The 64-year-old told the court that she had heard Mr Sheridan deny he had attended a swingers club during an executive meeting of the SSP in November 2004.
Responding to questions from Mr Sheridan, Ms Smith said: "You said you had never been to a sex club. I am absolutely clear about that. I was sitting next to you."
She added that Mr Sheridan had also told the meeting: "They would never find a shred of evidence."
Mr Sheridan asked the witness: "Could you have been confused?"
Ms Smith replied: "No, not at all. I don't think anybody could have been confused."
She also said there was "a heated and acrimonious atmosphere at the meeting".
The court also heard from 60-year-old Gordon Morgan, who was assistant treasurer of the SSP between 2003 and 2006.
He said the party was on the verge of bankruptcy at the time of the executive meeting in November 2004.
Mr Morgan, who was a founder member of the SSP, told the court that there had been a "division" between its elected MSPs since 2003.
Mr Sheridan asked Mr Morgan to describe the nature of the SSP during this period.
He replied: "Factioned. Groupings had been established and actions were being taken by groups of people together, not necessarily in the interests of the party.
"It was very clear that there had been a division between the MSPs elected.
"Frances Curran, Rosie Kane and Carolyn Leckie were acting together, socialising together, acting as a sub-group together and being derogatory towards both Tommy Sheridan and Rosemary Byrne."
He said financial pressure intensified this as there was a threat that people may lose their jobs.
Mr Sheridan denies making false statements as a witness in the defamation action on 21 July 2006.
His wife denies committing the same crime on 31 July 2006 after being sworn in as a witness at the civil jury trial.
The trial before Lord Bracadale continues.
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