The success of Extinction Rebellion, a British campaign of civil disobedience aimed at addressing the climate crisis, has been something to behold. In April, the group, which was formally launched only last October, blocked Waterloo Bridge, which spans the Thames, for more than a week. Across London, activists glued themselves to buildings, climbed on trains, chained themselves to company headquarters, and occupied key intersections, leading to some thousand arrests and messages of support from around the world. The Metropolitan Police commissioner, Cressida Dick, said that she had never encountered a protest like it. By the end of the month, Extinction Rebellion activists were meeting with Sadiq Khan, the mayor of London, and on May 1st, in accordance with one of their demands, Members of Parliament declared a climate and environment emergency, becoming the first national legislature to do so. In June, M.P.s agreed to another Extinction Rebellion request: to convene a citizens’ assembly, made up of a representative sample of the British population, to discuss the climate crisis. Although the assembly’s recommendations will not be legally binding, as the protesters wished, Extinction Rebellion’s language and its policy agenda have moved into the mainstream at remarkable speed.

On July 15th, the group began its next wave of protests: simultaneous week-long uprisings in Cardiff, Leeds, Glasgow, Bristol, and London. Each involves a sailboat parked on a busy street (“The Seas Are Rising and So Are We,” the slogan goes), along with a certain amount of annoyance and disruption. But, after the dramatic road-and-bridge seizures of the spring, the atmosphere of Extinction Rebellion’s summer demonstrations has been gentler and more celebratory. On a warm, sunny afternoon this past week, I visited a small park opposite the Old Vic Theatre, on the south bank of the Thames, that is serving as the base for the group’s current activities in the capital. Solar panels had been erected and a jazz band was playing on a stage lined with a pink banner that said, “Frugality, Humility, Empathy.” There were about sixty tents and a couple of hundred people resting and chatting, listening to the music. A young couple slept, entwined, next to a copy of “Jane Eyre” open in the grass. A box of food donations contained tangerines, oat cakes, and raspberries. Under some trees, a group was engaged in a “deep ecology” counselling session and a father was making a cardboard boat with his daughter, who seemed to be about five or six years old and was wearing her school uniform.

Signs of anarchy were polite in the extreme. “If your comrades wear masks or carry tools, don’t disrupt them,” read one rule, taped to a banner near the park gates. Under a white gazebo, a man in a red shirt was giving an introduction to a few dozen new Extinction Rebellion volunteers. The activists were advised not to give their names or any other information when challenged by the police, but the instructor suggested that replying “No comment” was a bit cold. “I couldn’t really say” was a better response, he told them, or “I don’t know.” Then walk away.

Extinction Rebellion claims to have affiliates in more than fifty countries. Last week, three American philanthropists—Trevor Neilson, Rory Kennedy, and Aileen Getty—set up the Climate Emergency Fund to support similar protest organizations, and pledged an initial five hundred thousand pounds to the group. (New York and Los Angeles both have branches of X.R., as it’s known, for short.) The campaign describes itself as a “self-organizing system,” but it is also the brainchild of a small group of experienced British radical activists. One of its founders is Roger Hallam, a fifty-three-year-old organic farmer from Wales, who is also a postgraduate student of theories of social change. Another is Gail Bradbrook, a longtime anti-fracking and tax-avoidance campaigner, who has a Ph.D. in molecular biophysics. Bradbrook and Hallam met in person for the first time in early 2017, not long after Bradbrook returned from a psychedelic retreat in Costa Rica, where she took ayahuasca, iboga, and kambo, in search of some clarity in her work. Bradbrook had been involved in the Occupy movement and campaigns around peak oil, but they failed to take off. “I was just sort of, like, fed up with failure,” she told me. “I was willing to just try anything, really.” Together, Bradbrook and Hallam sketched the outlines of Extinction Rebellion. In April, 2018, the strategy of conducting a peaceful, mass campaign of civil disobedience—Bradbrook and Hallam speak about converting a critical mass of 3.5 per cent of the British population, more than two million people—was formally approved at a meeting of about fifteen activists at Bradbrook’s house in Stroud, a market town in the Cotswolds with a strong ecological scene. Last summer, the first X.R. campaigners toured more than a hundred village halls and community centers, urging people to accept that the natural world is in a state of emergency. The group’s first demand—“Tell the truth”—is in many ways its greatest.

On Tuesday, Bradbrook, who is forty-seven, took the stage just after 5 P.M., wearing a turquoise top, flared jeans, and a large earring fashioned from a sparrow’s wing. She is a slight, elfin figure, with a Yorkshire accent. She addressed the park for about forty minutes, darting from the alienating spirit of competition inherent in capitalism to the Shambhala warriors of Tibetan Buddhism to the question of disabled access at X.R. demonstrations. One of the group’s strategic successes has been to make protests safe and welcoming for families, by consulting with the police before carrying them out. (I took my two young daughters on an X.R. march for clean air in East London, where I live, last week.) Another aspect of the group’s appeal has been the way that it acknowledges the private, and often paralyzing, emotions that come from thinking about climate change and ecological destruction. “I absolutely fucking love sparrows,” Bradbrook said during her speech, explaining her earring. “House sparrows were in packs in my parents’ garden.” Since the seventies, British house-sparrow populations have declined by half. “Every time I think about it, I want to cry. I miss them so deeply,” she said. Bradbrook likes to speak about the necessity of grieving for the elements of the natural world that have been lost. “It’s really unhinging and unsettling when you’re in the middle of it,” she told the crowd, to sporadic nods of recognition. “Love has a cost, and it’s grief. Because we will always be separated from things we love. That’s the nature and price of life, right? But, when you love something deeply, then you’re courageous.”

Earlier that day, six Extinction Rebellion protesters had been arrested after chaining themselves to the entrance of a cement factory in East London. Richard Walton, a former head of counterterrorism for the Metropolitan Police, has described the group as “anarchism with a smile,” whose underlying intention is to break up the state. (The X.R. protests in April are estimated to have cost around twenty-eight million pounds in lost earnings and extra policing.) It’s true that the founders of Extinction Rebellion have an extreme, anti-capitalist vision of what they want society to look like. “I want to live in a beautiful, nature-filled world, and, if we get shot on the streets fighting for it, so be it,” Bradbrook said in the park. “I’m willing to have that happen. I’m not calling for it to happen.”