Abroad, this has been fuelled by the wave of protest, revolution and war which since 2010 has swept across the Arab world, a reminder to all seemingly entrenched regimes of the precariousness of power. At home, pressure for political reform, prompted by economic transformation of the cities and disgust at corruption, has grown.

From Zhongnanhai, the Beijing compound of the party leadership, certain forms of protest appear to threaten the fabric of the state itself. In Tibet, the melancholy regularity of self-immolation by fire demonstrates how far the local population is from accepting Han colonisation. And a more militant form of Tibetan Buddhism than that preached by the Dalai Lama is infiltrating other parts of the country.

In the western region of Xinjiang, Muslim Uighurs continue to mount violent protests against Han domination. In 1933 and 1944 the weakness of central rule allowed the local population to declare a Republic of East Turkestan. That lesson is not lost on the CCP.

Christianity does not present the same secessionist challenges. But its links with the outside world worry a leadership which easily imagines that it is surrounded by hostile powers bent on its overthrow. 

In Redeemed by Fire, his book on Protestantism in modern China (Yale University Press, 2010), Lian Xi writes of a movement marked by "a potent mix of evangelistic fervour, biblical literalism, charismatic ecstasies, and a fiery eschatology not infrequently tinged with nationalistic exuberance". That makes for a volatile mix. Far greater numbers of Protestants belong to unregistered churches than to those affiliated with the government-controlled Three-Self — self-governing, self-financing and self-propagating — Patriotic Movement (TSPM). The former enjoy strong support in the US, where some Evangelicals envisage Christianity's becoming China's dominant religion, thus turning the country into an ally in the struggle against radical Islam.