Sheffield Doc/Fest and Channel 4 welcomed Oscar-winning director Michael Moore back to Sheffield, 18 years after his first visit. Voted one of "The World's 100 Most Influential People" by Time Magazine, he is widely regarded as one of the most important filmmakers working in documentary. Michael talks to Ralph Lee, Deputy Chief Creative Officer at Channel 4, about his latest film, Where to Invade Next?. which opened this year's Festival, as well as looking back over his hugely successful career. Supported by Channel 4.