In their tiny restaurant opposite the Emirates football stadium in north London, Wei Guirong and her husband Song Yong do a thriving trade in the traditional snacks of Xi’an, the capital of Shaanxi province and home of the Terracotta Army.

They make their own flatbreads and stuff them with juicy pulled pork, stretch out ribbony noodles from a wheatflour dough and bathe them in sizzling oil awakened by chillies and garlic.