Drifting across the dewy lawns of London’s Kew Gardens, the unmistakable voice of Sir David Attenborough has caused countless passing visitors to do a double take. After all, it’s not every day you spot the 95-year-old naturalist and broadcaster perched casually upon the gnarled root of an old oak tree.

On this overcast spring morning, Covid restrictions have eased enough to venture on location with BBC Studios’ renowned Natural History Unit.

It’s a shoot that marks five years since filming first began for the forthcoming five-part BBC documentary series The Green Planet – a period of time that has seen the team travel the world, capturing footage of the rarest and most intriguing plant-life imaginable.

“The world has suddenly become plant conscious,” Sir David reflects as he adds there has been “a revolution worldwide in attitudes towards the natural world in my lifetime”.

We have seen, he explains: “An awakening and an awareness of how important the natural world is to us all. An awareness that we would starve without plants, we wouldn’t be able to breathe without plants.

“The world is green – it’s an apt name (for the series), the world is green. And yet people’s understanding about plants, except in a very kind of narrow way, has not kept up with that. I think this will bring it home.”

It’s a concept that the show’s executive producer Mike Gunton concurs with.

“The idea behind this was I wanted to do a Planet Earth for plants – because obviously your first thought with plants is, ‘It’s going to be like Gardeners’ World, it’s going to be dull’,” the Bafta-winning producer says, glancing over at Sir David as the broadcaster rehearses his lines.

“Planet Earth, I think, gives you a sense that there’s going to be some drama and some scale. It is constructed by habitat, so I wanted to replicate that. There’s tropical worlds, desert worlds, water worlds, seasonal worlds, and human worlds.”

As the first ever Creative Director of the BBC’s Natural History Unit, Gunton has played a pivotal role in the production of hit BBC documentaries including Planet Earth II, Dynasties and Africa.

It’s a proven track record that sees him ideally placed to take on the mammoth challenge posed by The Green Planet. Reuniting with Dynasties series producer Rupert Barrington, the forthcoming series – which premiered on the eve of November’s COP26 summit in Glasgow – will see Sir David return to our screens as series narrator.

“The thing we’re trying to do in this series is constantly get the sense that we’re not static, we’re not just observing, because the heart of this is that this is a dynamic world,” Gunton says.

And for Sir David, his hopes of what people will take from the series include highlighting the importance plants play in human life.

He describes the world of plants as “a parallel world on which we depend, and which up to now we have largely ignored, if I speak on behalf of urbanised man.”

“Over half the population of the world according to the United Nations are urbanised, live in cities, only see cultivated plants and never see a wild community of plants. But that wild community is there, outside urban circumstances normally, and we depend upon it. And we better jolly well care for it,” the TV veteran warns.

Recalling how the series proposal was met with the words “we’re ploughing a new furrow” from Sir David, Gunton says he knew the project needed to be an immersive viewing experience in order to capture the minds of viewers.

“The green ecosystems are an incredibly strong web which underpins all life – and because it’s so complex and so strong, it’s an unchallengeable Jenga tower,” says Gunton. “What’s been happening is that we’ve been pulling the bricks out, but because we’re plant-blind, we haven’t really cared or noticed that we’ve pulled these bricks out.

“As we know, with a Jenga tower, if you just pull that last brick out, the whole thing collapses. What we’re trying to say is, be more aware of those Jenga blocks, because if you knock down that tower, it’s curtains.”

Noting the ever-present challenge of bringing the natural world to life, Gunton explains how the unit developed never-before-seen technology, resulting in a new approach to filmmaking.

Based upon a widely-used technique known as time-lapse photography – a process by which a moving object is photographed consistently over a period of time and when played back, appears as a fast-forwarded video – the concept emerged after producer Paul Williams chanced upon a YouTube video uploaded by American visual engineer, Chris Field.

Already a fan of botanical photography, Field had tinkered with existing electronics to create a customised camera capable of capturing the movement of plant life. Together with the BBC’s in-house team, they set about developing the technology in order to not only capture a simple time-lapse, but allow viewers to travel along the rainforest floor alongside plants and insects.

“Someone like Chris Field in a shed somewhere will have this brilliant idea and develop some sort of prototype which we can then build into a more robust system like we did here,” says Gunton, voice tinged with excitement.

It’s a project that also saw the Natural History Unit embrace drone technology – a more eco-friendly and immersive alternative to helicopters. Harnessing the skills of two competitive first-person-view drone pilots, the drones were able to weave through the rainforest canopy at high speed, capturing footage unlike anything the team had previously seen.

Recounting how the five year production saw the team – including Sir David, travel the world in search of exotic plant life, it’s clear that age is but a number to the veteran naturalist.

“David is in his 90s, so we had to be quite careful about the number of locations and the amount of time away, but we managed to [go] to all the habitats,” says Gunton, listing off a swathe of trips across South America and Europe. “We’ve been to rainforests, deserts, water worlds, and the Arctic – we actually even went to the Arctic Circle.”

Describing how Attenborough’s icy trip took place a week before the first wave of Covid restrictions set in, the producer says the subsequent travel ban saw much of the series’ human episode shot right here in the UK – notably the Botanic Gardens at Kew.

“As we flew in, everybody was coming off planes wearing masks and the news was saying, ‘This is going to stop shortly’,” says Gunton, shaking his head in hindsight.

The team also travelled to Costa Rica to make the docu-series, visiting La Selva Biological Station – and what they saw there should bring hope, as the research centre has become famous for giving vast swathes of their land back to the natural rainforest.

“Plants will do the work for you if you just leave it alone – they will rewire land for you, and that’s what David is saying,” says Gunton.

“The planet heals itself, we just need to give it the chance to do it rather than always messing around, chopping and tidying up.”

The Green Planet begins on BBC One on January 9.