The battles were fought on social media as well as in the open, with dozens of accounts appearing on every network, dedicated to providing a narrative from the protesters’ point of view. The ubiquity of cellphones equipped with cameras meant that everyone could be a journalist. Everyone could get the news out. Nothing could be done behind closed doors, hidden away, or swept under the oriental rug.

Hence the scene at the subway station. Cameras don’t perform optimally when exposed to rapidly flashing bright lights. Rather than a disco, or an attempt to blind the opposition, it’s a gambit to prevent footage from leaking out and being published online. Both sides use it with varying results.

No-one can say for sure how many high definition CCTV cameras cover Hong Kong’s 427 square miles, but it’s estimated to be one for every 140 people – nowhere near the UK’s one per 11 citizens, but easily enough to identify demonstrators screaming defiance at the dragon.

And China’s facial recognition algorithms are legendary, able to detect individual facial features regardless of glasses, hats or masks, and positively identify 98.1 percent of human faces in under one second. If the extradition bill stayed in force, it seemed almost guaranteed that some of those who had protested against it, whether or not they were disguised, would eventually find themselves staring into a surgeon’s mask from the wrong side

Not everybody in Hong Kong is hot for democracy, and pro China demonstrations have been nearly as well attended as the pro-democracy ones. Not everyone is wearing their hearts on their sleeves, and among the anti-China agitators, typically aged between 18 and 30, an impromptu parallel lexicon has developed. Like Cockney rhyming slang, which allowed 19th century criminals in London’s east end to discuss their nefarious plans in public, the new Hong Kong argot empowers protesters to plan and coordinate without incriminating themselves or others.

Plans and accounts of deeds are sprinkled with negatives, which are to be discounted by the listener. Don’t meet me outside your apartment block tonight, would be an invitation to meet outside the speaker’s apartment block. A conversation which mentioned shopping or magic indicates protests or starting fires. I dreamed that I stabbed a policeman last night translates as I totally stabbed a policeman last night*. It’s not particularly sophisticated, but it doesn’t need to be. It’s old school infosec, which speaks to the paranoia of not knowing who to trust, and whether the old lady standing next to you at the bus stop is an informer for the state.