Guardian editor Alan Rusbridger has praised the "first class investigative reporting" of Nick Davies following news that Downing Street head of communications Andy Coulson had resigned.
Coulson's exit follows hundreds of Guardian stories on phone-hacking and the News of the World which have questioned the official line that just one 'rogue reporter", Clive Goodman, was involved in the affair.
Resigning today, Coulson said: 'Nothing is more important than the Government's task of getting this country back on its feet.
"Unfortunately, continued coverage of events connected to my old job at the News of the World has made it difficult for me to give the 110 per cent needed in this role.
"I stand by what I've said about those events but when the spokesman needs a spokesman it's time to move on."
Rusbridger said: "This is the result of first class investigative reporting by one Guardian reporter, Nick Davies, sustained over a very long period of time.
'From the moment he revealed the secret payout to Gordon Taylor in July 2009 it was obvious that Andy Coulson's position was untenable. But this is not the end of the story by any means.
'There are many outstanding legal actions, and uncomfortable questions for others, including the police."
Speaking on a Guardian video this afternoon Rusbridger said: "I think News International must be wanting the pain to end. There are a number of legal cases coming down the slipway and I think the question for them is if they're really trying to get to the bottom of what happened, what are they going to do about the legal cases and is it true they're paying the former private investigator who went to prison, Glenn Mulcaire's legal costs at the moment?
"Because on one hand they're saying they want to get to the bottom of it and they have zero tolerance to wrongdoing and yet with the other hand people suspect that they are paying the one person who has the evidence in order not to reveal it in court. That is again an unsustainable position.
"I don't know anybody working in Fleet Street who believes that an editor could've remained in ignorance. I think it's surprising that David Cameron has stuck by Andy Coulson this long. If news reports were to be believed, as late as Wednesday evening he was still trying to convince him to stay and couldn't see the need for him to go."