Aweaving string of twinkling blue light is cascading down Ben Nevis, reflected in the waters of the loch below like a river of light. The drone camera catching the whole scene at nightfall sweeps in close – and suddenly the true nature of the “river” is revealed. This tumble of light is being created by a very long line of people swaying from side to side, each holding a lantern above their head. Even more surprisingly, one of those furiously swaying people is me. If it all looks beautiful in the film, it certainly didn’t feel beautiful in the moment. I’d spent two and a half hours on the ascent and was standing in a muddy mulch, freezing cold, painfully aware that I had to get back down Britain’s tallest mountain in the dark. When the director shouted, “Let’s do it again”, I desperately wanted to shout, “Let’s not!” Instead, I swung my eco-friendly light for all I was worth, joking with the young medical students beside me that we thought we’d signed up for a gentle evening stroll, not a through-the-night marathon. We were among 150 people recruited by Green Space, Dark Skies, a five-month-long live arts project that’s been running this year. Altogether 11,000 people have taken part, swinging their geolights around 21 of the UK’s most stunningly scenic locations, documented by director Mark Murphy. This Sunday’s Countryfile will be devoted to the lumenators, with films from the four finales being broadcast: as well as Nevis there’s Scafell Pike in the Lake District, Snowdonia in Wales and Slieve Donard in Northern Ireland. “This is high-end, cinematic art,” Murphy told us as we gathered at basecamp in mid-September. It wasn’t so much about us getting our names in lights, more that we were going to be the lights. “Some of you might not even feel like artists,” he continued, as we munched on energy-boosting venison casserole. “But once you get up there, and certainly by the time you come down, you’re going to feel very different.” Since I managed to pull a muscle in my knee, I certainly did feel very different on the way down: but all artists have to suffer. After a brief rehearsal in a field (“Swing your light in a seamless arc around your body”), we were dispatched to the rocky pathway. I was soon at the rear of the column, and quickly came to the notice of the mountain rescue team charged with helping stragglers. Initially I thought they were homing in on me because I was the Guardian journalist. “Don’t know anything about that, love,” one said. “You’re just very slow.” Thankfully, the movie location was “only” halfway up – “only” still being 2,200ft above sea level. By the time I staggered on to the muddy marsh, lantern at the ready, darkness had begun to fall. The vast mountain’s brooding magnificence loomed above us, so gorgeous it seemed a travesty to imagine that we humans – with our lights, cameras and drones – could in any way improve on nature. Green Space, Dark Skies is all about access to such landscapes. It was inspired by the 90th anniversary of the Kinder Scout trespass, when around 400 people marched on an area of the Peak District not legally accessible. It was an act of civil disobedience aimed at democratising the moorlands, which in those days were no-go areas for all but privileged grouse-shooters. The trespass is credited with leading to the creation of Britain’s national parks. Today, the issues around access are very different, says John Wassell, who dreamed up Green Space, Dark Skies more than two years ago. But they’re still entirely relevant. The focus in 2022 has been on who actually owns land, who can roam on it, what relationship humans have with it. “We wanted to enable people from cities and areas of dense population, as well as people with disabilities, to enjoy the countryside,” says Wassell. Among those climbing Nevis were members of Glasgow All Nations Sport Arts Recreation. As we negotiated the rocky path, manager Shazia Malik explained that their organisation was aimed at giving youngsters, especially those from ethnic communities, the chance to take part in sports and arts events. From that point of view, Green Space, Dark Skies scored full marks. “We’ve got 15 people here today,” she told me. “For them, it’s a phenomenal experience. They’re people who wouldn’t ordinarily have the chance to take part in an art film. They’re going to remember this for a long time.” With a budget of £5.6m, mostly given by the governments of the four UK nations, Green Space, Dark Skies wasn’t cheap. In part, says Wassell, it was devised to provide opportunities for creatives whose livelihoods had been undermined by Covid. Also, says programme director Sam Hunt, it was to celebrate collaborative creativity. Performance artists worked alongside technicians and scientists to produce the dramatic, light-filled films: engineers from Siemens helped create for the outdoors what Coldplay have been doing over the last few years for their illuminated concerts, using computer-driven LEDs. Although it seemed like a long, dark haul on a windswept mountainside to me, I’m assured by Nathaniel Fernandes, who developed the technology, that we would have been stuck on that hillside a great deal longer had it not been for the fact that the technicians could tweak the lights how the director wanted. We were a motley crew of all-comers, certainly not dancers: the ability to manipulate the lights, says Fernandes, was essential. “You’re going to be blown away by what you’ve created when you see it,” Murphy said as we did yet another take. At the time, I was just trying not to be blown away literally. But I have to admit, there is a certain satisfaction in not only managing to climb halfway up a mountain but having that endeavour preserved for posterity, thanks to a few sweeping waves of a lantern under the watchful eye of a buzzing drone. Countryfile is on BBC1 on 30 October. Visit greenspacedarkskies.uk for more details