A revelation that gives hope to Tommy Sheridan

Even in a case bristling with tales of betrayal, illicit sex and visits to swingers' clubs, one detail lodged itself in the minds of the reporters at the perjury trial of Tommy Sheridan.

Bob Bird, the editor of the Scottish News of the World, told how he had been ordered to strip to his underpants by an informant before he was allowed to view a secretly filmed video exposing the alleged dishonesty of the socialist firebrand.

The meeting came amid attempts by Rupert Murdoch's newspaper to overturn its legal humiliation at the hands of the former leader of the Scottish Socialist Party, who had won £200,000 damages from the title in 2006 during a defamation action over claims he had committed adultery.

During the ensuing perjury trial – where the Crown accused Sheridan of lying on oath during the earlier case – the High Court heard Sheridan's former comrades say he had admitted to visiting a sex club in Manchester; Anvar Khan, a News of the World journalist, say she had visited the sex club with him and had an affair with him; and a former candidate say she had had an affair with him. The jury also heard about the tape. In one of the most bizarre episodes in the hearing, Mr Bird described how he was summoned to an address in Pollok, Glasgow, in a series of "cloak and dagger" instructions by an anonymous caller who claimed to have vital information on Sheridan, but wanted to be sure the journalist was not secretly recording their meeting with a concealed "wire".

News of the World subsequently paid George McNeilage, Sheridan's best man, £200,000 for the tape.

For reporters in the press gallery, Mr Bird's willingness to strip to his briefs was evidence of a veteran professional's determination to get to the bottom of a story. Records of the perjury case show he was unable to obtain copies of some emails from his own IT department.

Sheridan's defence team had sought emails from News International relating to its alleged hacking of his phone and its contract negotiations with Ms Khan.

News International supplied some emails but Mr Bird, testifying under oath, repeatedly said others had been lost on the way to India. The police also disclosed some emails from News of the World to the defence.

News International now says Mr Bird unintentionally misled the court, but insists that all the emails sought by the defence were disclosed to it either by the newspaper or the police.

Sheridan's legal team suspects that more information should have been disclosed, and plans to launch an appeal in the hope of springing Sheridan from Barlinnie jail, where he has begun a three-year term.

There may be more twists and turns in the long-running battle between the socialist politician and the world's biggest news organisation.