Glenn Greenwald, the journalist who broke the Edward Snowden leaks story, says his mission is to hold power to account. Is this a journalistic crusade that has gone too far?

Thanks to Edward Snowden's leaking of American intelligence secrets, the whole world now knows the extent of US-UK surveillance of global phone and internet traffic. Have the revelations flagged up a corrosive infringement of individual liberty, or undermined efforts to protect the world from terrorism? HARDtalk speaks to journalist Glenn Greenwald - he broke the Snowden story. His mission, he says, is to hold power to account. Is this a journalistic crusade that has gone too far?