Timothy Garton Ash introduces the subject of freedom of speech and why it is more important than ever in today's internet-connected world. Professor Garton Ash sets out the arguments for why we need free speech, including for the sake of diversity, good governance and the search for truth. He argues that as smartphones and the web change our communications, we need a set of principles which govern free speech more than ever as this essential human right comes under attack. Drawing on research behind his book on the subject, he identifies three main threats. The first is what he calls the heckler's veto: if you shout loudly enough you can restrict free speech. The second is the offensiveness veto: if you cry 'I'm offended' you can restrict free speech. The third is the assassin's veto: if you say that, we will kill you. Produced by Nina Robinson