Permanently changing an audience's point of view, on the other hand, is a little trickier. For all of Munden's obvious sympathy, I didn't, at first, hold out much hope for the Rainbow Tribe. Even as I muttered liberal platitudes to myself ("It takes all sorts", "Live and let live"), I couldn't help snagging on a submerged uneasiness about their uncomplicated zeal. I don't know whether it's the covert thread of hope in their predictions of imminent catastrophe or their ceaseless self-congratulation, but there is something unappealing there, whatever one thinks about ecological evangelism. When Rainbow Lizzie announces that the "economic situation is just going to collapse", you suspect that she has her fingers crossed; she wants the globe to join her in bankruptcy.
But, little by little, Marc Munden's film eroded such suspicions. It helped that his film was funny, even if some of the laughs were a little dismissive. In one scene a young woman addressed the collective as they discussed whether to open a bank account: "If you want to be right on" she said, "then the one to go for is the Co-op. If you want to be practical then the nearest Co-op is in Islington right? And I'm sorry, but I fink if the Co-op were that together they'd have a branch in Camden." Later two Rainbow Warriors wielded their dreadful French on a local resident in an attempt to get her to sign a petition, persisting long after comprehension had curled up and died. The prospects for Warrior expansion into Europe did not look good.
It was also clear that John Major's characterisation of them as shiftless scroungers is a little wide of the mark. They may be irritatingly pious, and they may sing truly dreadful protest dirges ("We are a circle, we are a circle, with no beginning and never ending" - tune to fit the words) but they are also energetic, principled and determined. Active citizens, you could say. Their incredulity that the Criminal Justice Bill should have passed into law without widespread protest made you uneasy in a different way, an uncomfortable reminder that a society should be judged by how it accommodates its critics, not by how efficiently it suppresses them.
Last week Trial and Error gave the police a hard time in two accounts of alleged miscarriages of justice. Last night the BBC contributed to television's continuing supervision of the criminal justice system with Rough Justice (BBC1). The feel of the programmes is identical, from the title sequences to the casebook prose style ("Saturday, 23 May... a warm spring day...") but Rough Justice relied a little more heavily on contradictory expert opinion, a little less on digging up new facts. Even so, they made a fair case that Paul Esslemont's conviction for the brutal murder of Carl Kennedy, a three-year-old boy, was unsafe. You couldn't entirely blame the police for believing Esslemont had committed the crime, even if they had to ignore some inconvenient facts to protect that belief. But your thoughts about the rest of the judicial system were less charitable. Why does it take a television programme to make you feel reasonable doubt?