If you were wandering round Bankside on Saturday night you might have been bemused to see words appearing on the facade of Tate Modern and wondering if someone spiked your drink. But there was nothing to fear as it was just MC Yan, who rocked China by being the first to use Chinese characters in his graffiti, bringing Laser tagging, the new, high-tech future of graffiti, to London. Part of the Red Mansion Foundation's Down......