The Scottish News of the World editor told how he stripped to his underwear at a meeting with a man who claimed to have evidence that former MSP Tommy Sheridan lied during his defamation case.
Bob Bird, 54, said he received an anonymous phone call from a man after former Scottish Socialist Party (SSP) MSP Sheridan won the case against the paper in 2006.
A "cloak and dagger" meeting was arranged and Mr Bird met a man who turned out to be Tommy Sheridan's best man George McNeilage at an address in Pollok, Glasgow, where he was asked to remove his clothes. The court previously heard that Mr McNeilage was worried that Mr Bird would be "wired".
Mr Bird told the High Court in Glasgow: "He said `I'm Tommy's best man`, at which point my blood ran cold as I thought Tommy Sheridan was going to burst into the room with a video camera."
Mr McNeilage then showed him a videotape and asked for £250,000 for it, the court heard. Mr Bird said he considered the tape of interest.
Earlier in the trial, Mr McNeilage told the court that the Sunday newspaper paid him £200,000 for video footage he secretly filmed of a man alleged to be Sheridan in November 2004 in which he confesses to claims about his private life.
Sheridan and his wife Gail, both 46, are accused of lying under oath during Sheridan's successful 2006 defamation action against the News of the World.
They deny the charges against them.
Sheridan, a former contestant on Celebrity Big Brother, won £200,000 in damages after the newspaper printed allegations about his private life.
The indictment against the Sheridans contains three charges in total, two of which are broken down into subsections. It is alleged that he made false statements as a witness in the defamation action of July 21 2006.
He also denies a charge of attempting to persuade a witness to commit perjury shortly before the 23-day trial got under way.
Mrs Sheridan denies making false statements on July 31 2006, after being sworn in as a witness in the civil jury trial.
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