At first it looked as if the fears of managers at Aeon, the Japanese retail group, might prove unfounded. Early on a Saturday, 3,000 angry protesters appeared outside its Jusco shopping centre in a suburb of the eastern Chinese port city of Qingdao but marched past without testing the lines of police sent by local officials.

The respite was only temporary, says Hiroshi Ono, Aeon’s director of business planning in the city. By late that September morning, an even larger crowd was back to protest against Tokyo’s purchase of a group of disputed islands in the East China Sea. This time protesters surged through the building’s doors and across its more than 60,000 square metre floorspace in a frenzy of smashing and looting. Staff fled and the Chinese store manager escaped with the help of security guards and police.

The scene, echoed that same day at Japanese businesses in the suburb and in a handful of cities across the country, came as a stunning challenge to assumptions that have underpinned business and economic ties between China and Japan. Past diplomatic crises have never provoked public protests of such scale or fury and have had little impact on commerce. When it came to Sino-Japanese ties, Chinese analysts used to say: “Politics are cold, but economics are hot.”