Hong Kong’s unique brand of autonomy has been a gift for China. The city has been a channel for the world’s most populous nation to get moderately richer without Beijing having to relinquish control over its economy and people. It is no longer essential to the mainland’s future prosperity, however. Stripping it of the right to be treated differently from the People’s Republic, as the United States has proposed, only shows how disposable that special status is.

The nearly universal agreement to consider Hong Kong distinct from China after Britain handed the territory over in 1997 has served four main functions. All are becoming less relevant. The first is the trade in goods. China’s container ports are now sufficiently big and bustling that Hong Kong only accounted for less than 10 per cent of shipments by volume in 2018, whereas before the global financial crisis its share was more than twice as much.

Then there’s the Asian financial hub’s role as a spigot for capital movement. That’s still important, but China relies less on such flows these days. Foreign investment was equivalent to around 15pc of fixed-asset investment in 2000; last year it was roughly 1.5pc. Some, in any case, consists of Chinese funds that leave and return dressed up as foreign money to get tax perks and other benefits. That transfer of value from the many to the few is hard to defend.

Hong Kong’s special status also made it a launch pad for China’s attempts to internationalise its currency. That project has been a failure. The currency remains stuck at less than 2pc of global payments, according to network operator Swift, and less than 2pc of global central bank reserves, based on International Monetary Fund data. Companies have used Hong Kong as a place to raise capital, but that is now available domestically too.

Politically, maybe the most important contribution Hong Kong’s freedom makes is to serve as a tentative advertisement to Taiwan, the independently governed state China would like to reabsorb. Even there, the return on investment is dwindling. A Pew survey this month found that only 36pc of Taiwanese respondents support closer political ties with the People’s Republic, compared with 79pc who favour closer ties with the United States.

Being positioned outside China’s capital controls remains one of Hong Kong’s important attractions. Beijing hasn’t worked out how to turn mainland cities like Shanghai and Shenzhen into gateway regions, because of contradictory policy initiatives – on one hand, a drive to open up and attract foreign capital and knowledge, and on the other, a desire to keep capital and media controls intact. There, though, Hong Kong’s success may even have held China back, by making those difficult decisions too easy to shirk.

None of this is to say Hong Kong doesn’t matter, or that the loss of its freedoms wouldn’t be a tragedy. It does, however, make the place a poor target for reprisals against the People’s Republic. The enclave is unique only because it has rights China has chosen not to give to its other cities. That is a choice, and nothing more. Hong Kong is the most appealing way into China’s economy, but no longer the way to its heart.