Demand Grows for Global Ban on 'Killer Robots'

The United Nations’ special rapporteur on extrajudicial executions has joined calls for a moratorium on so-called ‘killer robots’ - automated weapons systems which critics fear may one day operate independently from human commanders. It may sound like something from a science-fiction movie - but campaigners say the threat is real and the robots already exist. Henry Ridgwell reports from London.