Glenn Greenwald: 'I almost missed out on Snowden story'
14 May 2014 Last updated at 21:31 BST
A year ago journalist Glenn Greenwald was planning a trip to Hong Kong to meet an anonymous source who claimed to have evidence of government surveillance on a massive scale.
Of course that source turned out to be National Security Agency contractor Edward Snowden - and their revelations created shock waves in the US and abroad.
In his new book No Place To Hide, Greenwald describes his collaboration with Mr Snowden and discusses the debate they prompted.
He spoke to Laura Trevelyan on BBC World News America.