David Cameron's former communications chief Andy Coulson has been charged with perjury in connection with the former trial of Scottish Socialist Party leader Tommy Sheridan.
The former News of the World editor was detained for questioning at Govan police station in Glasgow earlier on Wednesday by officers from Strathclyde Police.
Coulson was detained in London on Wednesday by Strathclyde Police and arrived at Govan Police Station in the south side of Glasgow later in the day.
The 44-year-old gave evidence in Sheridan's perjury trial at the High Court in Glasgow in December 2010.
Operation Rubicon detectives have been looking at whether certain witnesses lied to the court during Sheridan's trial as part of a "full" investigation into phone hacking in Scotland.
Sheridan was ultimately jailed for three years in January last year after being found guilty of perjury during his 2006 defamation action against the News of the World.
He had been awarded £200,000 in damages after winning the civil case but a jury at the High Court in Glasgow found him guilty of lying about the now-defunct tabloid's claims that he was an adulterer who visited a swingers' club.
The trial, which lasted almost 12 weeks, was one of the longest of its kind in Scottish legal history.
The former Scottish Socialist Party (SSP) leader represented himself after parting company with QC Maggie Scott.
He was convicted of five out of six allegations in a single charge of perjury relating to his evidence during the civil action at the Court of Session in Edinburgh.
His wife Gail was on trial along with him but was acquitted of lying to the court during his successful defamation action against the News of the World in 2006.
He was released from jail in January after serving one year of his sentence and vowed to continue the fight to clear his name.
More than six hours after Coulson was detained, Strathclyde Police released a statement on their Facebook page which said: "A 44-year-old man has been arrested in connection with alleged perjury before the High Court. A report will be submitted to the procurator fiscal."
They later added: "To be clear and to avoid confusion, the 44-year-old male has been arrested and charged with alleged perjury."
A Crown Office spokesman said there was no legal obligation for Coulson to stay in Scotland, and he was free to return to his home in London.
He said no date had been set for any court appearance.
Coulson, then employed by Downing Street as director of communications, told the Sheridan trial in December 2010 that he had no knowledge of illegal activities by reporters while he was editor of the News of the World.
He also claimed: "I don't accept there was a culture of phone hacking at the News of the World."
Coulson was arrested last year in relation to Scotland Yard's long-running investigation into phone hacking at the newspaper.
He was held in July on suspicion of conspiring to intercept communications and corruption, and had his bail extended earlier this month.
Coulson resigned as editor in 2007 after the paper's former royal editor Clive Goodman and private investigator Glenn Mulcaire were jailed for phone hacking.
In May that year, he was unveiled as director of communications and planning with the Conservative Party.
He quit his role as Downing Street communications chief in January last year after admitting the News of the World phone-hacking row was making his job impossible.
Sheridan's solicitor, Gordon Dangerfield, said Sheridan would be appealing against his conviction in due course.
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