Smiling, Li Na walks over to the window of the 54th floor of the Westin Hotel in the bustling city centre of Chongqing. She has just returned from a family holiday on the tropical island of Hainan and already has a double rendezvous: with Chongqing and a brilliant blue Mercedes-Benz GLC. With a clap of her hands, she bids farewell to her husband and two children, who ride the lift all the way to the top with us to marvel at the dizzyingly high pool. “Bye,” says Li Na in Chinese. “Mummy has to work.”