It was May 2018 when the man first asked Nur to spy for him. The message came, as usual, via WhatsApp and was assiduously polite. Nur seemed like a good citizen, it said, but as a Uyghur living in Turkey, he must do more to prove his loyalty to China. “We see you as an educated and important person,” the next message read. “So we have chosen you for a special job.”

All Nur needed to do, the man continued, was to attend meetings of other Uyghurs in Istanbul, make inquiries about certain people and then pass the information back to him.

Nur protested that he was too busy, that he was already loyal, that he might get caught by the Turkish police. Then he closed his WhatsApp. The messages frightened him and so did the man, who was now the only link to his parents in the autonomous region of Xinjiang, home to the majority of China’s 11.3 million Uyghurs.

The messages kept coming every few days, and soon their tone changed. “You are a smart man,” one said. “You need to think about your family. You are there, but they are here, and if you refuse to do this, you could put them in a very dangerous situation.”