What is journalism for? To inform and bear witness, uncover inconvenient truths and hold power to account? Those are surely values most of us share, but have we collectively lost faith and trust in the news and those who report it? Stephen Sackur speaks to Alan Rusbridger- who edited the UK’s Guardian newspaper for 20 years in the midst of a digital revolution, which transformed the news business forever. If the established media is no longer trusted, who is to blame?(Photo: Alan Rusbridger in the Hardtalk studio)