No walk, as far as I am concerned, is ever wasted. In contrast, for example, to a car journey. In a city - especially one dominated by cars, by individualistic rather than collective, private rather than public modes of transport - it is walking that habitually makes me feel alive. It makes me feel both vitally connected to the city's ceaseless circuits of energy and, at the same time, delicately detached from them. Stimulant, then, and narcotic.