There's one inevitable question, at every Q&A session, at every film festival, for every documentary filmmaker: "Tell us, how did you come across this story?"

In the case of Upstream Battle, the question will be like this: "Where did a filmmaker from Germany hear about this conflict between Native American tribes and an energy corporation, taking place in one of the most remote areas of the United States?" Well, the answer is simple: in Scotland.

A very good friend in Edinburgh deserves all the credit for the existence of this film. Stan Blackley specialises in environmental PR work, and he told me about a couple of tribal delegates who were coming to the UK to take on an energy giant, ScottishPower. In 2005, this Glasgow-based utility was one of the 25 largest in the world. Native Americans travelling half-way around the globe to fight for their river -- it truly is a David-against-Goliath story of today's world.

Stan was helping the tribes reach the British media, and I flew to Scotland to see what was going on. For some reason, I instantly connected to Merv and Wendy George (pictured right), to Ron Reed and Craig Tucker, to Richard Myers and Jeff Mitchell.(pictured above right) It soon became clear that all of them would have to be part of a documentary, but I had no idea that this would keep me busy for the next three years.

What did I know about the "American Indian"? Only what the European media had told me: that they still existed, stuck in reservations away from their old homelands; that they had huge problems with unemployment, poverty, and drugs; but some tribes had started very successful casinos. So I guess I knew a little more than those people in Glasgow who asked the visitors if they still lived in tepees.

Yet, our first research trip to the Klamath River in Northern California surprised my partner Magdalena and me in many ways. These tribes still inhabit a good part of their ancestral territory. In fact, the first white settlers didn't show up there before the 1850s. Many tribal members withstood the Christian missionaries and have managed to keep their traditional ceremonies going without interruption. Although their grandparents were sent to far-away boarding schools and punished for speaking their own language, people can still speak Yurok, Karuk, or Hupa today. Yet, Merv races jet boats and plays the drums in a rock'n'roll band. "It's all about balance," he explains.

But access to the tribes wasn't as easy as it first seemed. I'll soon tell you more about this -- and how we convinced the energy company to be part of  Upstream Battle.