The last column about the Guardian's stories of surveillance by the NSA and GCHQ on 23 September 2013 was three months after the first of the series. The reason I waited to write was to allow the dust to settle a little.

That autumn the Guardian was fighting a tough battle in the UK. The bulk of the press had lined up with the government to accuse the Guardian of arrogance or treason in publishing these stories, based on tens of thousands of secret documents disclosed by the NSA whistleblower Edward Snowden. Much dust has now settled – if not the final specks. It has been an extraordinary few weeks and while this column usually concentrates on the Guardian's errors, it would be a little odd not to revisit the Snowden story after the Guardian has won the Pulitzer prize. Yes, the Pulitzer prize, shared with the Washington Post.

Why was the Guardian eligible for a set of prizes that have been running in the US since 1917 and are probably the world's most sought-after awards for journalism – not to mention letters and music? This is part of the covering letter to the organisers from the Guardian: "The Guardian US was established in 2011 to cover US and international news for an American audience. As a New York-based company – incorporated in the US as Guardian News and Media LLC – we maintain a growing and largely autonomous editorial presence with a US staff of 60, a bureau in DC and reporters across the nation. The newsroom produces news articles, opinion, live-blogs and interactive and multimedia content that reaches over 20 million online US readers each month. The series of NSA stories – enclosed for consideration – were reported, edited and published by Guardian US staff."

Therein also lies the reason that the Guardian was able to publish the entire series of stories about the Snowden revelations.

The heavy-handed British government told the Guardian it stood in danger of prosecution in the UK unless it destroyed computers upon which the Snowden documents were held. After the largely symbolic act of destruction in the Guardian's basement in King's Place, publication was continued through the Guardian US website. That's why the Guardian was able to submit 14 pieces of work, including video that began with the first story on 5 June 2013, NSA collecting phone records of millions of Verizon customers daily, and ended on 18 December with Obama review panel: strip NSA of power to collect phone data records .

Those headlines neatly describe the trajectory of public and political opinion in the US. As Alan Rusbridger, the Guardian's editor-in-chief, wrote to editorial colleagues on winning the award: "The Public Service category prize is the most prestigious of all the journalism prizes – rewarding 'disinterested and meritorious public service' with the Pulitzer Prize Gold Medal. The NYT won it for the Pentagon Papers in 1972, the Washington Post for Watergate in 1973, the Boston Globe in 2003 for exposing sexual abuse by Catholic priests.

"The citation reads: 'Awarded to the Guardian US for its revelation of widespread secret surveillance by the National Security Agency, helping through aggressive reporting to spark a debate about the relationship between the government and the public over issues of security and privacy.'"

Rusbridger's note went on to thank, along with Edward Snowden, a team of journalists in the UK, the US and Australia.

In a further sign of the public mood in the US, Glenn Greenwald and Laura Poitras had earlier cleared immigration at John F Kennedy airport in New York without a hitch as they arrived to share a George Polk Award for national security reporting with Ewen MacAskill of the Guardian and Barton Gellman of the Washington Post.

In the UK there had been little noticeable change in attitude to the Guardian's revelations – at least in the media – until the British Press Awards on 2 April 2014, where the Guardian won newspaper of the year and also received the award for its website. Given the feelings of some editors it was a generous decision.

The Guardian is still absorbing the lessons of the NSA stories but a point that Rusbridger now emphasises in public talks, especially to journalism students, is that reporters, regional or national, must learn the basics of encryption if they are to protect sources. Before the Snowden revelations, that would have seemed eccentric.

- Chris Elliott/The Guardian © Guardian News and Media 2014