Andy Coulson, Prime Minister David Cameron’s former Director of Communications, was taken from his London home on the morning of May 30 in a dawn raid and driven over 350 miles to a police station in Glasgow, Scotland.

There he was questioned for 12 hours about the evidence he’d given at the 2010 trial of former Scottish Socialist Party (SSP) leader Tommy Sheridan.

Under the Scottish judicial system, someone can be detained for up to 12 hours without being considered under arrest. After that they have to be charged, released, or a senior officer has to authorise a further 12 hours.

Coulson was already on police bail, after being arrested July 8, 2011, over phone hacking and police bribery allegations relating to his former position as editor of Rupert Murdoch’s News of the World tabloid from 2003 until 2007.

Last week, officers connected with Operation Rubicon arrested Coulson and charged him with perjury. Rubicon is the Scottish police investigation set up to probe into accusations of perjury by witnesses at the Sheridan trial, along with the allegations of News International’s phone hacking and possible illegal payments to police in Scotland.

In Scotland, the charge of perjury can carry a hefty penalty for anyone found guilty. Coulson reacted by insisting he will “vigorously contest” the charge.

His charging opens the way for the criminal and illegal activities of Murdoch’s News International to be aired in open court.

At the time he is accused of having perjured himself, in 2010, Coulson was Cameron’s spin doctor in the newly-formed Conservative/Liberal Democrat coalition. He had been summoned to give evidence at Sheridan’s trial for perjury.

Sheridan was tried in connection with a successful defamation case he had brought in 2006 against News International’s now defunct News of the World Sunday tabloid.

Found guilty by an 8-6 verdict and jailed for three years, Sheridan served only one year of his sentence before being released earlier this year.

Coulson told Glasgow’s High Court during Sheridan’s trial, “I don't accept there was a culture of phone hacking at the News of the World.”

Asked by Sheridan, who was conducting his own defence, “Did the News of the World pay corrupt police officers?” Coulson said, “Not to my knowledge.”

Soon after the trial ended, the full story of News Internationals’ phone hacking and police bribery operations began to unfold. This undermined the case made against Sheridan, who has argued that the verdict against him is now unsafe.

Last July Strathclyde Police’s Chief Constable George Hamilton confirmed that Coulson was among those under investigation after “allegations that witnesses gave perjured evidence in the trial of Tommy Sheridan and into alleged breaches of data protection and phone hacking.”

After ten months, Coulson is the first to be arrested in relation to the case. According to a source close to the police, “Operation Rubicon has uncovered widespread malpractice—in connection with the Tommy Sheridan case but also in connection with phone hacking”.

The source continued, “Our main focus has been on who ordered illegal activities. It is fair to say we are confident that there will be further arrests.”

Police believe more than 200 people in Scotland have been potential hacking victims after their names were found in the notebook of Glenn Mulcaire, the private detective jailed in 2007 for phone hacking on behalf of the News of the World. Former Scottish first Minister Jack McConnell, First Minister Alex Salmond's aide Joan McAlpine and actor Sean Connery are among those who have revealed they were hacked.

At his trial, Sheridan’s legal team requested access to emails sent between the Scottish News of the World and Mulcaire. They were told the emails could not be accessed because they were lost in an archive in Mumbai, India. Sheridan’s lawyer, Aamer Anwar, said at the trial, “Bob Bird [then editor of Scottish News of the World] gave evidence that emails could not be disclosed as they were lost in an archive in Mumbai. We now know this to be totally untrue… The police spent three years and £2 million on investigating Tommy Sheridan.”

Anwar submitted a dossier to Strathclyde Police including information relating to statements made by Coulson, Bird and former Scottish News of the World news editor Douglas Wight during the 2010 trial. It included a page from Mulcaire’s notebook containing Sheridan’s mobile phone number and PIN, evidence transcripts from News of the World employees given at the trial, and extracts from a “blue book” of instructions to private detectives from News of the World journalists, including former editor and News International chief executive Rebekah Brooks.

Anwar was supported by Labour MP Tom Watson, who said in Parliament, “I think the Sheridan trial was unsound and may need to be revisited.”

Watson wrote to the Information Commissioner and established that News International’s e-mail archive was never transferred to India. He told the BBC, “The jury was not in full possession of the facts. I think Tommy Sheridan was wronged. Had they been in possession of the email it might have materially affected the outcome of the trial.”

Watson subsequently co-wrote and published a book with the Independent newspaper’s Martin Hickman entitled Dial M for Murdoch, which includes a section looking at the events surrounding Sheridan’s trial.

Coulson quit as editor of the News of the World in 2007, after Mulcaire, along with the paper’s former royal editor Clive Goodman, were convicted and imprisoned. In May that year he was appointed director of communications with the Conservatives, until being forced to resign in January 2011.

Cameron has repeatedly defended Coulson and his arrest for a second time is a disaster for the government, which is already confronting damaging revelations regarding its intimate relations with Murdoch at the Leveson inquiry into media ethics.

The Tory party leaders are not the only ones who will be worried at Coulson’s arrest. Sheridan could only have been brought to a retrial in the first instance because of the rotten political character of the SSP. The SSP’s leading personnel colluded with the News of the World and the police to secure a guilty verdict against their former leader. Of the 42 prosecution witnesses, over half were members of the SSP, including 16 former members of its Executive Committee.