Class reunions are popular in China and last night a group of former Wuhan University students met in a Shanghai restaurant for a meal of hairy crab and Great Wall cabernet sauvignon. Unfortunately for the diners, the most famous class member could not make it.

When they last met, Liu Qibing – the absent classmate – was an official at a little-known government agency in Beijing that deals in commodities. This weekend he is at the centre of what could become a large international trading scandal involving vast numbers of copper contracts on the London Metals Exchange.