It's all Muhammad Ali's fault.

The first documentary that Asif Kapadia remembers blowing him away on the big screen was When We Were Kings, the documentary about the Rumble in the Jungle, Ali's fight with George Foreman in Zaire in 1974. "Ali in that film," Kapadia says, "that's a movie star. A superhero. Nobody should ever pretend to be Muhammad Ali. That played a big part in me thinking 'I don't want anyone pretending to be Ayrton Senna.;"

So when it came to making Senna, Kapadia had a model to follow. He brought his own style to it, of course. There are no talking heads to be seen in Senna. "I started doing my research and I just thought this is the best set of rushes I've ever seen in my life. This is amazing. It's so obvious. Just let the footage tell the story.' I could easily shoot a few talking heads, chuck them in and say 'look, there I am'. I don't think it would make for a better film. Sometimes you have to take yourself out and trust the material.

"That is the director's job. To find the best way to tell the story. It was really hard to get people to believe in that idea. It took a couple of years. Not everyone would say it now, but at the time nobody wanted to do it. Now everyone thinks it was their idea."

The result was something truly cinematic. The same process can be seen in Amy. "Elevating them to the big screen there is another thing going on. Amy's songs if you've never heard them, they're amazing. And just getting that intimacy, just studying that face. The big picture behind not having talking heads is I just want to look at her. I just want to spend time with her. Her face is so expressive and her eyes are so bright at the beginning and so sad as you see the change."

That's the director talking. What about the rest of us? Why are we drawn to these real stories on the big screen? "I feel there's a gap somewhere in indie cinema and docs have plugged that hole. The independent cinema I grew up with - Jim Jarmusch, Spike Lee, Ang Lee, Hal Hartley - I don't know where those films are now. Movies have become comic books, visual effects-heavy things. And docs, because of the reality and hopefully because they have some sort of intelligence to them, seem to be plugging that hole."