At Harrods, one of London’s most upmarket department stores, Chunmei Pei, a twenty-something Chinese woman dressed in Stella McCartney platform brogues, tight jeans and a black Chanel backpack, walks around the shop floor. She is glued to her iPhone, juggling half a dozen WeChat messages with her clients. Ms Pei is a professional daigou: an overseas shopper who buys luxury items like watches, jewellery, clothes and cosmetics for mainland Chinese. Today one of her buyers is considering an ￡860 Dior “Diorosphère” chain necklace with a gold finish, while another wants a ￡1,500 Céline bag.

Most luxury stores do not allow photos or videos of the products for fear of counterfeiters, so Ms Pei is constantly updating her clients on the price, colour and product details with calls and live messaging. The chatting is endless and all part of the service. She spends at least 20 minutes at Céline while they search for a different colour of the bag and the buyer dithers. Once she gives the go-ahead for the purchase, Ms Pei arranges the sales-tax exemption, buys it on her card, packages it up and posts it. She does this for a fee she will not disclose, although daigou commonly charge commission of 5 to 15 per cent.

Consultancy Bain & Co estimates that daigou like Ms Pei accounted for Rmb34bn-Rmb50bn ($5.1bn-$7.5bn) of sales last year, equivalent to 12 per cent (at the upper end) of Chinese luxury spending. But that is a fall from 20 per cent in 2014, and Bain predicts that this will drop further as profit margins are squeezed and the Chinese government tightens controls over imports, including by daigou.