My legs shake as I climb the 100th step, scan the green-toothed horizon, see grey clouds snake through the unploughed hills of Inner Mongolia, coal breath poisoning Beijing from the north. (Chinese astronaut Yang Liwei looked in vain for the Great Wall from space, but American Space Station commander Leroy Chiao caught the sleeping dragon with a 180mm lens—ah, those Americans and their affinity for walls; ah, those Americans, lassoing the Wonders of the World from space.) And me, I’ve placed my hands on the ragstone of Londinium, wondered how anyone could think a wall could stop time and change? Herman, come from Germany as a young DP, props a piece of the Berlin wall against his open cottage door. The breeze, he says, is coolest in the morning.