The Daleks are obsessed with racial purity and dedicated to a policy of genocide: they represent the Nazis. The Jagrafess is a loathsome alien purveying useless information - which he has censored, rewritten and controlled: he represents a modern day media mogul. This is the theory of the US academic Marc Edward DiPaolo who has analysed the political content of five decades of Doctor Who. He finds that the Time Lord is a liberal, bohemian, pacifist environmentalist, and definitely anti-American. Is Doctor Who a closet radical? Laurie and Marc discuss the contention with journalist, broadcaster and some-time Dr Who script-writer Matthew Sweet.