It’s just before midnight, and I'm walking through Frankfurt, making the worst noise in the world. At this time of night, the banks of the river Main – Frankfurt is officially Frankfurt am Main – are usually deserted. There’s nobody to hear my awful, awful noise. The Museumsuferfest starts tomorrow. The riverside path is lined with tents and stalls and expensive-looking stages, and shadowy figures move between them. Some of them stop and watch as I approach. Who could blame...