Two thousand,five hundred kilometres from his home in rural China, just edging into his teens, Hai Weiliang stood on the docks of Kolkata. The light of his faith had led him there, abandoning his voyage home from the Haj pilgrimage, but now he had no idea which way to turn. Finally, a kindly cleric found him a cheap room at an inn near a mosque. Arming himself with a Chinese-to-English conversation book for travellers, Hai began conversing with local seminary students.

Fires would be lit across central Asia as his speech grew less hesitant.

Late last month, new evidence emerged on the brutal incarceration of thousands of Xinjiang residents at China’s internment centres, set up to stamp out religion-fuelled secessionism. Tajikistan and Kyrgyzstan felt compelled to use repression against resurgent Islamist networks, whose lethal reach extends from the Ferghana valley to Europe’s heartlands.

The extraordinary story of the Chinese Muslim teenager who arrived in Kolkata shows how India, a century ago, provided the intellectual ground from which this global jihadist movement grew.