You have to realize that, about 20,000 years ago, there was a cataclysmic event when an entire rock face collapsed and sealed off the cave. It's a completely preserved time capsule. You've got tracks of cave bears that look like they were left yesterday, and you've got the footprint of a boy who was probably eight years old next to the footprint of a wolf.

I'm trying to find these rare moments where you feel completely illuminated. Facts never illuminate you. The phone directory of Manhattan doesn't illuminate you, although it has factually correct entries, millions of them. But these rare moments of illumination that you find when you read a great poem, you instantly know. You instantly feel this spark of illumination. You are almost stepping outside of yourself and you see something sublime.

I couldn't roam wildly and speak secretly with villagers [in North Korea]. No way you could do that. And honestly, I didn't even try. I was realistic of what I could do and yet persuaded them into accepting numerous things that I shouldn't have filmed.

We were very, very lucky [with Tim White filmed making historic discoveries in the East African Rift ] . In 100 years, only three skeletal remains [of early man] were ever found at this site. This was the third one, and we were right there when it happened. In fact, when I first heard they had found something, I said, "Please stop it! Don't do anything right now. Let's do it tomorrow until we have unpacked our cameras and assembled our stuff.

Some of the most important caves, like Lascaux in the Dordogne region in France, have had to be closed down. There had been too many people allowed in, and they left a mold on the walls that is spreading and which can't really be stopped.

For a film I shot on the most difficult mountain on God's wide earth in Patagonia for a sequence where there was high probability some digital effects were needed, somebody made storyboards and I quickly ignored them, after half an hour I ignored them and I never used any digital effect.

Netflix trusted me in a way that was very, very pleasant.