David Cameron's former spin chief, Andy Coulson, has been detained on suspicion of committing perjury during the Tommy Sheridan trial in Glasgow's High Court.
The 44-year-old was held in London on Wednesday morning by officers from Strathclyde Police.
The former News of the World editor gave evidence in Mr Sheridan's perjury trial at the High Court in Glasgow in December 2010.
Sheridan was 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 after which he was awarded £200,000 in damages.
However, 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.
Coulson was arrested last year in relation to Scotland Yard's long-running investigation into phone-hacking at the News of the World on suspicion of conspiring to intercept communications and corruption and had his bail extended earlier this month.
During Mr Sheridan's trial he said he had no knowledge of illegal activities by reporters while he was editor of the News of the World.
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."
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.