Documentary profiling the work of Robert Rauschenberg, the influential American artist who was the first to win the Golden Lion at the Venice Biennale in 1963, and is said to have blazed a trail for creatives in the US throughout the 20th century. Rauschenberg's work has rarely been seen in the UK, but the Tate Modern is about to change that via a major new retrospective due to open this month. Ahead of the exhibition, Alastair Sooke travels to the east coast of the USA to talk to some of the people closest to Rauschenberg. His interviews provide a portrait of a man with boundless curiosity and a restlessness for experimentation, whose 60-year-long career saw him bridge the gap between the abstract expressionists of the 1950s, and the pop-art enthusiasts of the 1960s.