In a Hong Kong hotel room in June 2013, director Laura Poitras filmed a pivotal decision in recent history: Edward Snowden’s choice to reveal an extensive network of surveillance conducted by the US government against its own citizens. Since the revelations, Snowden has ended up in Russia where he has been granted political asylum. And Poitras, who turned the footage she shot of the former NSA contractor into the documentary Citizenfour, has also moved to Europe, through fears that she might be arrested in the US.

Citizenfour concludes a trilogy of documentaries Poitras has made that show the effect of 9/11 on America and the world: the first was My Country, My Country, about life in Iraq following the US invasion in 2003; the second was The Oath, about inmates at the US detention facility at Guantanamo Bay, Cuba. These films provide a powerful perspective on US policy in the last 13 years – in the case of Citizenfour, even some of Edward Snowden’s original detractors, like Hollywood mogul Harvey Weinstein, came to embrace its message. Weinstein told the BBC that he found Snowden’s actions “despicable” but after seeing Citizenfour decided that he would help distribute it. And now it's a leading contender to win the best documentary feature prize at the Academy Awards.

Tom Brook reveals how Poitras helped Edward Snowden tell his story – and the dramatic fallout they both continue to face.

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