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Andy Coulson had hoped he had drawn a line under the phone-hacking row when he resigned as editor of the News of the World in 2007 - but legal action against the paper by a number of public figures has led to a drip-drip of new allegations.

It is almost exactly four years since the culmination of the court case which brought the practice of phone-hacking at the News of the World to public attention.

The royal editor of the News of the World, Clive Goodman, was jailed for four months for tapping the phone calls of members of the royal family.

The Old Bailey heard that he accessed several hundred messages on the mobile phones used by aides to princes William and Harry. A private investigator, Glenn Mulcaire, was jailed too.

The paper's editor Andy Coulson resigned, saying he took "ultimate responsibility", though he said he had not known about the phone-hacking.

He and the News of the World's publishers insisted it was an isolated case - perpetrated by a single "rogue reporter" - but ever since then this has been widely disputed.

Nothing more was proven, despite inquiries by the police, the Press Complaints Commission and the Crown Prosecution Service.

In July that year, Mr Coulson was appointed as media adviser to the Conservative opposition leader, David Cameron.

Two years later, the story resurfaced with a story by Nick Davies, an investigative reporter at the Guardian.

He claimed to have uncovered evidence that the News of the World regularly used private investigators to hack into phones and that Scotland Yard had found the names of hundreds of public figures that had been targeted.

He reported that one of the victims in the original phone-hacking case, Gordon Taylor of the Professional Footballers Association, had received an out-of-court settlement to drop legal action that could have led to other News of the World journalists being named.

MPs on the Culture Media & Sport Select Committee held an inquiry, and Mr Coulson repeated his declaration that the royal phone-hacking had been an isolated incident.

"What we had with the Clive Goodman case was a reporter who deceived the managing editor's office and in turn deceived me. I've thought long and hard about it - I did when I left. What could I have done to stop this from happening?" he said.

"But if a rogue reporter decides to behave in that fashion, I'm not sure there's an awful lot more I could have done."

The MPs remained unconvinced. In their report, they said they thought it was "inconceivable" that no-one else at the News of the World knew what was going on, but they said they had seen no evidence that Mr Coulson knew phone-hacking was taking place.

Now the story has resurfaced again. Partly as a result of the Guardian investigation and further inquiries by the New York Times, several public figures - including the actress Sienna Miller, the actor Steve Coogan and the sports presenter Andy Gray - have begun legal action against the News of the World seeking compensation, claiming their privacy was breached by the paper.

Other public figures, including former Labour ministers Lord Prescott and Chris Bryant, are seeking a judicial review of the police handling of the investigation, saying they were not told that papers with their names on were found in the office of the private detective at the centre of the inquiry.

Earlier this month it emerged that, just before Christmas, an assistant editor of the News of the World, Ian Edmondson, had been suspended from active duties by the paper while it conducted its own internal investigation.

A spokeswoman for the paper said it had a "zero tolerance approach to any wrongdoing" and that if the allegation were proven, appropriate action would be taken.

And now the Crown Prosecution Service has asked a senior QC to re-examine all the evidence gathered by the police in their original inquiry.

In his resignation statement, Andy Coulson said he stood by what he had said about the events at the News of the World but the continuing coverage meant he could no longer devote 110% to his job at Number 10.

He is acknowledging what has become increasingly clear in recent weeks - that this story still has a long way to run.

And, as a spindoctor and former tabloid editor, he had the perfect phrase: "When the spokesman needs a spokesman it's time to move on".