His activism — and China’s pursuit of him — did not end once he moved to London. Last year, Hong Kong authorities put a bounty on Cheng and other activists, offering $128,000 for information leading to their arrest. Still, like many Hong Kong activists living in self-imposed exile in Britain, he hoped his newfound distance from the Chinese authorities put him far from their reach.

Last week, three men were charged in London with gathering intelligence for Hong Kong and forcing entry into a British residence. While the men have not yet been found innocent or guilty — the trial will not begin until February — the news of the arrests threw a spotlight on many activists’ existing concerns about China’s ability to surveil and harass its citizens abroad, particularly those who have been critical of the government.

A spokesperson for China’s Foreign Ministry on Friday denounced what he called the “false accusations” and “vile actions” of British authorities in taking the case. Last week, one of the accused men, a British former marine called Matthew Trickett, was found dead in a park while on bail. The death was categorized as “unexplained” by the police, which in Britain refers to unexpected deaths where the cause is not immediately clear, including suicide. During Trickett’s initial court appearance, the prosecutor said that Trickett had tried to take his own life after being charged.

Anxiety over the arrests has rippled through the broader Hong Kong diaspora in Britain, even among those who are not politically active.

“You can kind of expect something like that to happen, but it is still so surreal,” said Cheng, speaking from the central London office of Hongkongers in Britain, an organization he founded to aid new arrivals. Pinned on his sweater was a bright yellow umbrella, a symbol of the prodemocracy demonstrations that filled Hong Kong streets in 2014 and again in 2019.

China imposed a Draconian national security law in Hong Kong in 2020, granting authorities in the former British colony sweeping powers to crack down on dissent. In response to the law, Britain introduced a new visa for Hong Kong citizens. Since then, at least 180,000 Hong Kongers have relocated through the visa program. Many have rebuilt their lives in Britain and continue to participate in the prodemocracy movement from afar.

Britain’s Foreign Office said last week that the recent accusations of intelligence gathering appeared to be part of a “pattern of behavior directed by China against the UK,” which includes the bounties being issued for information on dissidents.

Thomas Fung, 32, hopes the arrests will mark the beginning of a concerted effort by the British government to combat Chinese repression. “We always knew there was some kind of intelligence, or some spying on people, or just monitoring of what we are doing here,” he said.

Fung came to England in 2012 to study accounting. He got a job in Oxford when he graduated and decided to stay. As Hong Kong’s prodemocracy demonstrations swelled, he felt compelled to show his support.

He participated in solidarity protests in London and later volunteered to help newly arrived Hong Kongers resettle. Eventually, he founded Bonham Tree Aid, a charity that supports political prisoners in Hong Kong. The first time his organization’s name was mentioned in a pro-Beijing newspaper in mainland China, he said, “I knew there was no turning back.”

Politically active Hong Kongers like Fung and Cheng are not the only ones who fear being targeted by Beijing. Families looking for better education and young professionals seeking job opportunities also feel threatened, said Richard Choi, a community organizer in the south London borough of Sutton.

Sutton is sometimes referred to as “Little Hong Kong” because nearly 4,000 former Hong Kong residents have resettled there since 2021.

Choi, 42, came to London in 2008 for work and now runs a Facebook group for new arrivals in Sutton. He carefully obscures the faces of the community in the photographs he shares, as many fear they are being monitored.

“I feel they are so nervous or have lost trust,” he said of the new arrivals. The community became even more nervous, he said, after Hong Kong passed a law known as Article 23 in March that carries penalties including life imprisonment for political crimes and extends to Hong Kongers abroad.

“Maybe there was a period where people relaxed a bit,” Choi said, but those with family in Hong Kong fear that if they return, they could be jailed. “They feel they have to behave and not say anything.”

Some in the diaspora remain vocal prodemocracy activists despite the risks. “I am very proud of my identity as a Hong Kong person,” said Vivian Wong, who moved to London in 2015 and opened a restaurant, Aquila Cafe, in east London in 2021.

The restaurant serves popular Hong Kong dishes and has become a place where members of the diaspora can gather for events and support one another. Inside, a noisy kitchen is run by chefs from Hong Kong slinging out steaming bowls of shrimp wonton soup and plates of crispy Hong Kong French toast stuffed with salted egg yolk.

Photographs of protests line the walls, and the blue flag of British Hong Kong flies over the cash register. Wong knows these symbols are seen by China as provocative, but she remains steadfast in her opposition to Communist rule.

“They try to threaten us,” she said, “but I am not afraid.”

This article originally appeared in The New York Times.