This isn’t about the extradition bill any more. It isn’t about police brutality. It isn’t even about links between the security forces and organised crime, or about the role of Chinese agents provocateurs. It has turned, rather, into a constitutional question.

Is Hong Kong truly a self-governing territory? Is “One Country, Two Systems” more than just a slogan? For the protesters – and for the broad mass of the population that sustains them – this is now about defending the constitutional freedoms that China promised to respect in the 1984 Sino-British Joint Declaration. For Beijing, the fear is that the civil disobedience might turn into a full-scale independence movement.

The issue that sparked the unrest has been all but forgotten. Back in the 1980s, when Deng Xiaoping was seeking to persuade Britain to relinquish the entire territory, rather than just that part held on a 99-year lease, he proposed a ban on extradition to mainland China as a way of reassuring the islanders. Earlier this year, in response to the murder of a Hong Kong woman in Taiwan by a Hong Kong man who fled back home, the authorities moved to close what they saw as a loophole.