The Great Firewall of China is one of the wonders of the modern world. Hundreds of thousands of censors are employed to ensure that as little as possible is published on the internet that might inconvenience or threaten the government. The tendency among western liberals and pro-democracy types is to suppose that this must make the state less efficient. But suppose the censorship is so fine-tuned that it actually strengthens the repressive apparatus by making it cleverer, rather than simply squelching all opposition?

The classic argument has always been that, compared with democracies, totalitarian states have always been less efficient and prone to making much larger mistakes, because in a society where the truth is dangerous, even the rulers find themselves operating in a fog of lies.

The Chinese government may have found a way around this. In a remarkable study published in Science, a group of researchers studied the Chinese censorship regime from the inside by setting up a social media website inside China, buying approved software, and asking the censorship authorities how they should operate it. As it drily reports: “The ‘interviews’ we conducted this way were unusually informative because the job of our sources was in fact to answer the questions posed.”

As well as this site, they also posted in various ways on 100 Chinese social media sites (and the two largest have more than half a billion users each) to see which messages got through.

The result, which confirms earlier results, is that you can say pretty much anything you like on Chinese media, providing that it does not lead to any kind of action. “Chinese people can write the most vitriolic blogposts about even the top Chinese leaders without fear of censorship, but if they write in support of, or [even] in opposition to an ongoing protest – or even about a rally in favour of a popular policy or leader – they will be censored.”

Even more subtly, the volume of protests is used to gauge whether any given leader is sufficiently unpopular that his removal will make things go more smoothly. In this way the information signalling part of a market economy is co-opted to the service of an authoritarian state. It turns out that you can say what you like – and this includes all the kinds of hashtag activism. All you may not do is influence events away from the keyboard, or even refer to them. If there is a news story that suggests there might be a role for protest in the physical world, all comments referring to it are removed, whichever side they take.

This study ought to be the final nail in the coffin of techno-libertarianism. Over the past few months there have been plenty of stories to remind us how loathsome the internet can be to women or anyone else singled out for bullying. But even when it empowers nasty people, this is forgiven or at least defended on the grounds that it empowers good people too. The Chinese example shows that it empowers nasty regimes as well as nasty people, providing they are subtle and intelligent enough.

It is also a blow at the idea of artificial intelligence and algorithmic censorship. If the internet is to capture information of use to the ruling party, it has to be operated by human censors. There are lists of keywords that will get a post blocked or at least reviewed, but these are very crude and easy to circumvent.

There is an improbable precedent for all this, from another ruthless imperial power that was setting out to impose itself on the world: the England of Elizabeth I. She also had a vast apparatus of spies and censors, although they were concerned with religious heresy rather than democracy. When she said that she “would not make windows into men’s souls” it seemed to be a great statement of tolerance, but it was in fact exactly the same as the Chinese policy: think what you like, providing you never dare act on it. This is future George Orwell never saw: a jackboot poised above a human face – and the face talks on and on about kitten pictures.