In Conversation With: Rob Petit

What drew you to Robert Macfarlane’s book, and when did you first conceive of adapting it into a documentary?

“The way into the underland is through the riven trunk of an old ash tree.” – this was the opening line of the book, and it gripped me… it was mythic and enticing. Shortly thereafter I was struck by the impulse that this very special book could also be a film. It was all to do with the direction of travel: into the void. These are the kind of stories I’ve always been drawn toward – ones that leave behind the world we know and enter one where we are the guests, the alien arrivals: from Narnia to Apocalypse Now and Fitzcarraldo. Robert Macfarlane and I had actually just completed our own ode to that Conradian notion of moving away from the familiar and into the strange by following the course of a river against its flow from floodplain to source for our project ‘Upstream’. Although Underland followed a downward trajectory, it still seemed like a logical extension of the idea of going upriver, and Robert had already cracked open a window into this subterranean realm so the temptation to follow with a camera was too much to resist.

What were the challenges of filming, in particular the scenes in the Yucatán caves and underwater laboratories?

The challenges were numerous. Before we even begun to think about how to film these spaces I had to find a cinematographer who didn’t balk at the idea of wriggling into the underworld, worm-like, with masses of delicate, expensive equipment. As soon as I spoke with Ruben Woodin Dechamps, I knew I’d found someone special: a supreme creative talent with a proper sense of adventure. The next stage was to embark on a caving expedition as a team, without kit, simply to learn how to operate underground. Then, slowly, piece by piece we started asking the questions: how would we light these places? How would we move the camera? What about crew size? How will we shuttle batteries to the surface for charging?

Despite the extensive preparation we did the Underland always has some surprises for us: in Yucatán for example there were pockets of the cave system that were very low in oxygen while in SNOLAB (the science laboratory two kilometres beneath the surface) the subterranean experiment we wanted to film was actually encased in an inaccessible chamber of ultra-pure water, so we had to look for creative solutions (combining, in that case, some painstaking model making with some extraordinary visual effects courtesy of VFX director Balázs Simon). In every location, we had to learn a new set of rules and rely on the expertise of our on-screen terranauts to guide us.

The themes of the film are vast, connecting ancient Mayan civilisations with the search for Dark Matter to explain our universe. How do you think underground spaces connect to these profound topics of human existence?

Macfarlane so elegantly answers this very question in the book by framing any journey into the Underland as a journey into ‘deep time’. By doing this, he argues that to descend into the Earth is to come to understand quite how far into the past (and future) our influence as a species can reach. So he casts us as the ‘ancestors-to-be’. I love this way of thinking and how it obliterates the short-termism that dominates much of our surface-based existence. But – it took a while to figure out how that beautiful, poetic idea could translate into something that we could feel on screen, in cinematic terms. The solution was to focus on three journeys that (as a whole) embodied the idea.

And so I wanted each of these journeys to follow a similar arc: beginning within the boundaries of a single discipline (archaeology, urban exploration or theoretical physics) and then each becoming (in its own way) a journey into ‘deep time’. Early in the development process I drew a sketch on the back of a napkin of these intertwining, colliding storylines. The drawing looked like a hastily scribbled vortex but people seemed to get it. The longer I worked on the project, and the more journeys we did underground, the more I came to believe that Macfarlane’s hypothesis was correct: to descend beneath the surface is to enter a totally different realm of time altogether, and with that a new form of vision can emerge.

When did you realise the film needed a voiceover and how did you approach the script for the narration? And what did Sandra Hüller bring to the project?

I knew from the beginning that we would need a storyteller, the question was how heavily we would need to lean on them. I co-wrote the narration with Macfarlane and we were both instinctively against the idea of having too much; instead we wanted the stories themselves to generate their own gravitational mass. So the narration evolved constantly in response to the edit, eventually finding its shape as a five act story structure. As soon as Sandra Hüller came on board we had a voice to write for and with it, also a sense of the balance between the ‘mythopoetic’ and the informational. I was keen for the narration not to refer to any on-screen characters, and sit instead above the action in a part-human space, as if it were the voice of a spirit dwelling in the deep time dark. The script took on a whole other life when Sandra stepped up to the mic and then again when composer Hannah Peel and sound designer Joakim Sundström folded her into the soundscape. The result is a sparse narration, but one who holds you, dreamlike, guiding you through the dark.

Underland screens from Friday 27 March.