David Cameron's ex-communications chief has been arrested again this morning on suspicion of perjury. Andy Coulson was head of comms for Cameron from May 2007 to January 2011, when he left the role over pressure surrounding further revelations of phone-hacking at News of the World during his editorship.

The case for which he was arrested this morning concerns the trial of Tommy Sheridan, the Scottish politician, for perjury.

Sheridan won a defamation action against News International in 2006, but was then accused of perjury in 2010 and convicted. Coulson gave evidence at the trial in 2010, and his testimony has now come under investigation.

Coulson was arrested last year in a separate trial: the ongoing investigation into phone-hacking at News International, for which he worked for many years.

He also gave evidence at the Leveson Inquiry earlier this month, and spoke of his 'reluctance' to take up the role with Cameron when it was first offered to him. Moreover, although News International continued to pay him for several months whilst he worked for Cameron, he has denied any suggestion of an improper relationship between the media owners and the Conservative Party.

Previously on Communicate:

Andy Coulson quits as No. 10 chief

Andy Coulson embarks on consultancy career

Coulson was "reluctant" about No. 10 role