In 2005, while living as a student in Hong Kong, I had a conversation with a classmate that betrayed the deep tensions between residents of the former colony and their cousins up north.
Over coffee with the Hongkonger, I mentioned plans to travel to the mainland. A pause. 'Be careful,' the girl warned ominously. The mainland, she relayed with a knowing nod, was not only filthy but full of thieves.
I was puzzled. Dirty? Maybe. Unsafe? Rarely. Had she ever visited? No, she replied. Why would she want to do that?
Seven years later, ingrained prejudices on both sides of the border have flared up spectacularly. On the mainland side, there's Peking University professor Kong Qingdong calling Hongkongers 'bastards' and 'dogs of British colonialists', and in Hong Kong the particularly rabid bunch who took out a full-page advert in the Apple Daily showing a locust gazing at the city's skyline.
The ad's message was clear: mainlanders who come to Hong Kong to give birth, shop, sight-see or work are pests. As Beijing is well aware, the ad reveals niggling insecurities.
The central government is confident that in the not-too-distant future it will be Hongkongers feeding off the mainland, not the other way around. The recent D&G controversy - in which one of the store's security guards stopped locals taking pictures while allowing mainlanders to do so - is a case in point.