Planet Earth II’s iguana hero.

We begin with a close-up of a marine iguana hatchling, followed by a close-up of the nearly blind snake that’s trying to eat it. The iguana freezes as the snake slithers right behind it. The music swells and … the iguana is off! This is just the start of what might be the most exhilarating nature clip ever filmed:

Like many of the best Planet Earth clips, this incredible footage is the result of the kind of extreme luck that only comes with hard work. A camera crew worked from dusk to dawn for weeks filming the exact spot, hoping something would happen, and if it did, that the camera would be in focus. As is often the case with the acclaimed series, they got their shot.

Ahead of Planet Earth II’s American premiere this Saturday night on BBC America — which debuts with the standout “Islands” episode — Vulture spoke with Liz White, the producer behind the episode and the iguana versus snakes clip. White explains exactly how the moment was captured, how the story evolved once they discovered the Galapagos Island’s “wall of death,” and what Hollywood blockbuster scores they used while editing.

I wanted to talk about the iguana versus snake scene because I believe is one of the all-time greatest filmed things. You were the producer of the episode, but that can be a malleable term. What was your role in the episode?

With this series, we had six different producers for six different episodes — each had a single producer. They wanted us to really immerse in one show, one habitat, so we could get under the skin of it. For me, that was three-and-a-half years about nothing but islands, trying to work out what stories to do. And I really, really wanted to do a Galapagos story. I was like, “You can’t do a show about islands and not do something in Galapagos.” Because my background is marine, I was like, “I don’t really want to do the finches or the turtles.” I’ve always thought marine iguanas were cool. I mean, their faces, they look like Godzilla and they swim and they dive. They’re awesome. It was a shoo-in.

The problem is, everyone’s seen marine iguanas before, so what can you do that’s different? I was having a brainstorm with one of our cameramen who lives out in Galapagos and he happened to say, “Oh, you know what I filmed a few years ago? The hatchlings. It’s really cool because they walk up on the plateau of the rocks and these snakes grab them.” It had been filmed twice before, but it never really had much coverage. So we came up with the whole story about how the marine iguanas are really successful at staying alive, and how that allows other animals to survive. We’ve got the crabs in there [who feed on the iguanas’ dead skin] and the smaller lizards who eat the flies that fly around the colony. We also expected to be filming hawks, birds, and snakes.

Did the story change when you got to the island?

The day we arrived to Galapagos — we were on the beach — and we saw a baby iguana caught by snakes. We were like, “Cool, we’ve timed it really, really well.” Still, there was a lot of scouting, with us going around and looking for where these hatchlings were coming out. You have no idea because the mother iguana laid its egg three months in advance. A lot of the time was spent standing at the top of the beach with a pair of binoculars just looking for teeny-weeny little black heads. Suddenly we’d see this little thing on the sand and then it’s like, “Oh my god,” everybody has to stand to attention and watch and wait and film and blah, blah, blah. That was our system because you can’t run across the sand. The Galapagos is very protected, so you can’t get too close to the animals. We had a park ranger with us and he was telling us where we could and couldn’t go. Most of the time you’re at the top of the beach, just waiting and watching.

Was there a breakthrough?

Quite early on, this little hatchling came out and it was wandering towards one particular rock wall, which we eventually started calling “the wall of death,” because when it got near the wall, a medusa’s head of snakes just poured out. We all just went, “Shit!” We’d been looking for snakes, and seen quite a few little individual snakes, but we realized there would be like ten snakes in any one crack. They’re really smart because all the iguanas from that side of the beach have to go past that bottleneck in order to get to the colony, so the snakes are always hanging out there because there’s more of a chance of getting a meal. That’s where we focused. We were like, we’ll do the wall because it’s way more interesting to see snakes crawling out of the rock rather than just a kind of ambush. We put pretty much all of our resources to just working that one area of the beach.

I’ve never seen that number of snakes together in one spot, and they’ve got really evil-looking little faces.

Do you see that and start figuring out a story? Like, “Okay, the snakes will be the villains.”

It wasn’t even as complicated as that. You look at the cracks and there’s like ten snake heads and you’re like, “Whoa, that’s a lot snakes.” It’s a no-brainer. I’ve never seen that number of snakes together in one spot, and they’ve got really evil-looking little faces. But, also, I want to argue the snakes’ case. There’s very little food for them. Even though, obviously, we tell the story from the marine iguanas’ perspective — and that’s pretty brutal, if you happen to get caught as a baby marine iguana — the snakes have got a really tough time. Once the marine iguana get to the sea, their life is fairly easy. It’s the most brutal life for the snakes.

They’re not actually that big. We filmed it all right down on the iguana’s eye level, where snakes look quite big. That’s the whole point. We put you into the iguana’s world. When you’re there as a human being, they’re not at all threatening, they’re not even that venomous. They’re not hunting together. There’s absolutely no pack hunting. Every single snake is out to get that meal for himself. We saw snakes bite other snakes. Literally, they are fighting each other to get that food. They totally are watching the sand. You could stand in front of them as a human and move your hands around near them and they won’t take notice. They don’t even take notices of larger lizards, because they are too fast. They’re totally waiting for baby marine iguanas.

What was your plan going in to actually shooting it?

We had quite a big shopping list. It was about three weeks long, and the first two weeks we did nothing but concentrate on the beach. The cameraman would sometimes go off and film, say, the lizards catching flies, but, for the core — like for me, the camera assistant, the ranger, and one of the cameramen — we constantly were stationed on the beach. Literally dawn till dusk. We’d get there as soon as possible in the morning because those iguanas can come out at any time. We reckoned there was probably more coming out in the middle of the day — because they’re cold-blooded and they need to warm up — but you just don’t know.

Sometimes a little hatchling would come out and if they went down towards the sea, some of them would just walk through completely boldly and make it straight down to the colony. Others would go towards the wall. The cameraman has to take a gamble and go, “Do you know what? I’m just gonna cover these snakes and hope that the iguana comes this way.” Sometimes it works and sometimes it doesn’t, and we can get anything from like one hatchling in the day to six or seven. An awful a lot of times there would be just one and we missed the moment, or it got through and we just didn’t get it.

We tried to maximize our chances by having two cameramen: One of them was shooting on a very long lens from a tripod so he would be able to get all the close-ups; and the other was using a hand-held system where he could actually walk around holding the camera and try running into position, in front of the shots. Some people think some of the shots are shot on a drone, but they’re not — that’s actually a cameraman holding it just above waist height. You’re not allowed to use a drone in Galapagos. We had to be active and flexible.

How close would the cameraman get when the iguana was running?

The rule in Galapagos is you can’t go within, I think, two meters of any wildlife. If any of the animals come closer to you, that’s fine. Sometimes they’d run past you really close, or even just walk past you really close. I remember sitting on the sand one day and one of them literally walked up and sat in my shadow. Also, when they’re running, you have no chance, you can’t keep up with them. They’re way faster than humans. A few of them we showed running at high speed, but virtually all of it is very much slowed down because you just can’t see the action otherwise.

Every single snake is out to get that meal for himself. We saw snakes bite other snakes. Literally, they are fighting each other to get that food.

There’s one that ends up being the focus with the incredible escape.

Yes, hero.

Do you remember that day or the moment when you captured that one?

I remember it fairly well. The thing was, there was no guarantee we’d actually really get the shots, because it all happened so fast. It’s only when you go back to the boat in the evening and you go through footage that you can actually see whether it’s in focus. This chase happened and the cameraman was swearing and going, “Oh, shit I don’t think it’s in focus.” In fact, if you watch the sequence, there are shots that are not in focus, where the focus is actually on the rocks behind and not iguana. Amazingly, where it comes into focus is just as the snake bites. It ended up being more tense at the end of filming because we’re suddenly going, “Well, that was amazing but we don’t actually know if we’ve got it.” It’s why we kept working for two weeks — to really make sure we had enough material.

Once you saw the hero’s escape was in focus, how did you start conceptualizing the piece with the editor?

From the beginning, I knew what I wanted, so it was a case of just trying to figure out how best to tell it. Specifically, in terms of the order of events — whether to start with one getting nailed or whether to let one go first — that was the debate between the editor and me. It’s like doing a jigsaw puzzle. Also, trying to make sure you’ve got the right bits to tell the story and the biological story. You want it to be a big, emotional piece where people are going to feel like they’re rooting for a character, but we also wanted to be able to have the stuff about the snake’s eyes.

When I talk about the scene it’s hard not to describe it as if it’s about a person. What do you think grounds it in such a visceral human reality?

It’s in the images. The fact that they’ve got four legs and they stand up on their back legs to run, and that they’re cute, massively makes it an easier story. Or that last shot, where the snakes fall back and the little one is left basically gripping by his little fingernails — it does have a clear movie parallel. If it was a different kind of animal, it probably wouldn’t have the same results, but the fact that there’s something about it that’s almost quite human makes a big difference. Also, human beings are normally fearful of the idea of giant snakes. We didn’t plan for it to be that kind of story — we expected it to be an ambush story — so it takes on its own organic feel. We were just really lucky that the ingredients came together.

How does the music get incorporated?

The music was absolutely beautiful for it. We could have killed the sequence with the music by making it too in your face. We used all sorts of music, anything from Mad Max to Batman, when we were editing a temporary piece. This is the one that the guys really, really had to work on to get it just right. You’ve just got to get the right amount of tension because it is quite a high-octane sequence from the beginning. The very first take when the iguana comes out, he’s running for his life. The music had to add the tension. If you watch it without the music, it hasn’t got anywhere near as much impact.

You want it to be a big, emotional piece where people are going to feel like they’re rooting for a character.

How did you ultimately score it to have the proper amount of tension?

I worried a little bit when I first watched it. I said, “The first part of the music is a bit too stop-start” and that “at the end the music needs to carry it so it feels like you were climaxing towards something.” It was simple things, like when the iguana gets caught by the snakes, you could literally stop the music there and everybody’s emotion would just go, Ugh. But there’s a slightly discordant string that carries on and then it gets more and more discordant. It’s a music cue that is basically telling everybody, “Keep watching, because it’s not over yet.” As a result, there’s very, very little commentary. You don’t need it. It’s much better to just let it all unfold. Like if we had it going, “Oh, look, there’s a snake behind him!” it would lose all its magic. Also, the fact that the shots run long. A lot of his shots are left as is, and that adds to the suspense. Like the shot in the beginning with the little one walking, and then one snake comes in, and then two snakes, and then three, that is all about the fact that you don’t change shots. You let that one shot run and let it develop and let it develop, and that in many ways puts in natural tension.

Though Planet Earth II hasn’t come out in the states yet, this clip especially has gone viral in the U.K. Considering how long it took to make, what has that felt like?

It’s just been lovely that that particular clip seems to have suddenly resonated on many different levels. Obviously you’ve got the funny parodies, some of which are brilliant. I still want to call the first iguana Fiona thanks that the Ozzy Man parody. It’s something around the series that has been really nice, that people see the animals and then they relate to them in their own world. That’s exactly what we wanted. We want people to feel more connected to nature by seeing these animals and their stories and feeling a sense of empathy for it. They’re thinking, God, yeah, actually that animal has got a really hard life. It does summarize quite neatly what the series is about. It’s about putting you into the animal’s world and making people feel as if they’ve got a better understanding of what those animals go through to live their lives.

It both connects your life to the iguana’s and the iguana’s life to yours — like we are all essentially just trying to wriggle through.

It’s been really sweet. On Twitter there are kids all over the U.K. playing snakes and iguanas. You see people doing these little funny things online about, “Oh, I know what that iguana feels like.” For us as filmmakers that’s what we wanted to see — for people to watch nature and relate.