Most people spend their lives walking on a flat, smooth world, every bump and ripple rolled concrete. or tarmac flat, every incline tamed by escalators and lifts. The most significant hazards are curbs, forcing the lazy leg to lift, and dog shit – rare these days – forcing the feet to skirt. And so it’s a shock to visit the developing world – which is pretty much still the third – where the world is never flat, a place with trash, broken glass, excrement of all kinds. Here, a bin is a wall at the end of your garden; where the trash, when put in huge metal skips, is pulled out and searched for garbage gold; places where the streets look like a used nappy Stalingrad. When you walk there, every footstep is a trap, every innocent puddle a claymore mine, not water, but animal blood, or some horror ooze. Nails stick up of pieces of wood, and shards of everything threaten to rip at your feet. And then there are the cats and the rats and creepy crawlies. There is no going on your phone, your feet require constant attention, holes in the street that will swallow you up, pavements two feet high to topple off. But slowly, your flat-footed feet, and your flat world brain, begin to connect with where you are, and with football like control, your feet begin to duck and weave and dribble. Like a ghetto John Muir, who saw all nature in the head of a pin of lichen, you see the messages in a tapestry of filth; you no longer trip, or stumble, or leap, but can read what route to take. This is a lesson, so see it for what it is, a lesson in chaos.