Alan Rusbridger, editor of The Guardian, writes: A little over two months ago I was contacted by a very senior government official claiming to represent the views of the prime minister. There followed two meetings in which he demanded the return or destruction of all the material we were working 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.

The mood toughened just over a month ago, when I received a phone call from the centre of government telling me: “You’ve had your fun. Now we want the stuff back.” There followed further meetings with shadowy Whitehall figures. The demand was the same: hand the Snowden material back or destroy it. I explained that we could not research and report on this subject if we complied with this request. The man from Whitehall looked mystified. “You’ve had your debate. There’s no need to write any more.”

During one of these meetings I asked directly whether the government would move to close down the Guardian’s reporting through a legal route – by going to court to force the surrender of the material on which we were working. The official confirmed that, in the absence of handover or destruction, this was indeed the government’s intention. Prior restraint, near impossible in the US, was now explicitly and imminently on the table in the UK. But my experience over WikiLeaks – the thumb drive and the first amendment – had already prepared me for this moment. I explained to the man from Whitehall about the nature of international collaborations and the way in which, these days, media organisations could take advantage of the most permissive legal environments. Bluntly, we did not have to do our reporting from London. Already most of the NSA stories were being reported and edited out of New York. And had it occurred to him that Greenwald lived in Brazil?