The Guardian's editor Alan Rusbridger has said he was contacted by a senior government official, claiming to represented the views of David Cameron, that ultimately led to government agents destroying hard drives at the paper's London office.
After two meetings, the official demanded the return or destruction of all whistleblowing material that was being worked on.
“The tone was steely, if cordial, but there was an implicit threat that others within government and Whitehall favoured a far more draconian approach,” Rusbridger wrote.
Things got worse a month ago when he received a phone call from the centre of government, telling him: "You've had your fun. Now we want the stuff back."
Rusbridger had further meetings with “shadowy Whitehall figures” who wanted the Snowden material back or destroyed.
It became even more sinister when Rusbridger asked directly whether the government would shut down the Guardian's reporting through the courts.
The official confirmed this was the government's back up plan.
Rusbridger explained that the Guardian was not constrained to doing its reporting from London. Most of the NSA stories were being reported and edited out of New York and Brazil.
He said that any court order would fail to stop the presses because it would only apply to the UK.
However, the man called in two GCHQ security experts and they oversaw the destruction of hard drives in the Guardian's basement.
Rusbridger pointed out that the whole exercise was pointless as the data still existed and will be examined by journalists outside the UK.
He warned that soon it will be impossible for journalists to have confidential sources, but at least it is now clear the Heathrow transit lounges are not safe places for reporters.
Yesterday, David Miranda, the partner of Glenn Greenwald, who has done most of the work around the NSA revelations, was held at Heathrow for nine hours without legal representation on terror charges.