A couple of months ago a small tree came down on Tooting Common, blocking one of the paths. In line with current environmental thinking, and because there was plenty of room, the council left it where it fell, and since then people have been going around it. Now the curving course of the detour is firmly established, though the 'ghost' of the old, straight path, quickly filling in with grass, can still just about be seen.
These kind of accidents have always determined the course of paths and tracks, and in some cases the resulting kinks have survived for hundreds of years. As the landscape historian Oliver Rackham says in his seminal book, The Illustrated History of the Countryside,"Ancient roads, Roman or otherwise, usually have a course consisting of a series of small wobbles... over the centuries, travellers have gone round fallen trees, sloughs, holes, muckheaps... and dead horses; they have continued to go round after the obstruction has disappeared."