David Cameron’s former communications chief, Andy Coulson, has been detained on suspicion of committing perjury during the trial of former Scottish Parliament member Tommy Sheridan.
The 44-year-old was detained in London this morning by officers from Strathclyde Police.
Mr Coulson gave evidence in December 2010 at Mr Sheridan's perjury trial at the High Court in Glasgow. It is understood he is now on his way to the Scottish city.
Mr Sheridan was ultimately jailed for three years in January 2011 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.
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.
A Strathclyde Police spokesman said: "Officers from Strathclyde Police Operation Rubicon detained a 44-year-old man in London this morning under Section 14 of the Criminal Procedures Scotland Act on suspicion of committing perjury before the High Court in Glasgow.
"It would be inappropriate to comment any further at this time."
Mr Coulson, then employed by Downing Street as director of communications, told the 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." Mr Coulson was arrested last year in relation to Scotland Yard's long-running investigation into phone-hacking at the News of the World.
He was held in July on suspicion of conspiring to intercept communications and corruption and had his bail extended earlier this month.
Mr Coulson resigned as editor of the News of the World in 2007 after the paper's former royal editor Clive Goodman and private investigator Glenn Mulcaire were jailed for phone hacking.
Only months later, 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.
Mr Sheridan's trial, which lasted almost 12 weeks, was one of the longest of its kind in Scottish legal history.
The former Scottish Socialist Party 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.
PA