Anders Hammer moved to Hong Kong in 2019 to capture a David versus Goliath battle on camera, filming pro-democracy protesters in the city taking on autocrats in Beijing.

Little over a year later he became an inadvertent protagonist in that fight, when his low budget documentary Do Not Split won an Oscar nomination.

Chinese authorities, apparently enraged or worried by the platform the star-studded evening might give the film, and by long-deleted comments from best director nominee Chloé Zhao, has reportedly told local media not to broadcast the ceremony live, and play down all coverage of the awards.

Hammer is bemused at the lengths to which China has gone to stop its citizens catching even a brief glimpse of his latest film. In the rest of the world, that move has earned him the type of press coverage he could never have dreamt of.

“We are part of a category, short documentaries, which is not normally one that gets most attention [in Oscar coverage],” he said. “It’s ironic Beijing is actually at this point promoting our documentary.”

His half-hour exploration of the protest is beautifully filmed in a fluid, intimate style that takes the viewer into the intense heart of street demonstrations.

Millions marched in peace through Hong Kong’s streets in the summer of 2019, originally spurred by anger at a law that would have allowed the city to extradite people to face trial in the mainland’s opaque and judicial system.

As the protests expanded into broader demands for democracy, the police response became increasingly brutal. By the end of the year students were besieged in their university campus, stuffing molotov cocktails to take on police who were now liberal with their use of tear gas, rubber bullets and even live ammunition.

Coronavirus brought the public demonstrations to an abrupt end, and soon afterwards Beijing passed a security law for Hong Kong that effectively ended the city’s limited autonomy and has been used to crush the pro-democracy movement.

Key figures are mostly in jail, in exile or awaiting trial. Even protest slogans and songs have been banned under the new legislation. The Norwegian director believes Beijing’s fear of a short documentary, even after this comprehensive crackdown, is a tribute to the protest movement’s enduring power.

“It was the biggest revolt against Beijing, and the political leadership [there] in a very long time,” Hammer said. “I think that the [Chinese leadership] is very afraid that this could spread in some way and that you would see similar actions being taken in mainland China … the fear that someone will be inspired to try to do the same.”

The star of the film, if that is the right word for a documentary about a grassroots protest movement that deliberately eschewed leader figures, is Joey Siu. She talks eloquently about how she became an accidental student activist, setting aside plans to teach as the fight for her city’s future became more urgent.

Most of the young protesters on the frontlines chose to stay anonymous over fears of retaliation that have proved well founded. Siu decided to go public, and continue to speak out, at huge personal cost.

“Ever since 2019, when I first went public [with my identity], I have been receiving a lot of harassment … and my personal information, or even information about my family members have been posted and circulated online,” she said.

The video that ends the film is the last one Siu recorded in Hong Kong. She realised she was being followed, and watched friends arrested – some as they tried to flee – and soon after decided to leave for the US.

Yet somehow, like others in the movement, she clings to hope that while they may have lost the battle for Hong Kong, they still have a chance in the long-term war for democracy.

“We understand that the situation in Hong Kong is not going to become any better, we’re pretty sure that the Chinese Communist party is not planning to restore any kinds of freedom or rights that we used to enjoy,” Siu said.

“But we are very determined to explore other possibilities to sustain the struggle.” The new focus includes lobbying for political support, organising protests where that is still possible – beyond China’s borders – and building solidarity.

The name of the documentary is taken from a protest motto, emphasising the need for unity in the face of pressure from Beijing. That commitment endures, and she is grateful that a film she took part in to document their struggle, is now also helping support it.

“All of us understand that this is going to be a very long and very difficult battle so we are trying our very best to sustain the momentum that we built in 2019,” she said.

“The Oscar nomination has galvanised a lot of attention from people across the globe, who might not have been paying attention to what has been going on in Hong Kong.”