Simon Davies examines the most unruly of all our human rights. On a hot summer day in 2001, Derek Smith (we'll call him that to preserve his privacy), unexpectedly discovered a closed circuit television (CCTV) camera scrutinising him from a neighbour's roof. Smith was relaxing at the time by the side of his backyard pool, watching over his two young daughters as they played in the shallow water. He gazed with growing horror at the device, which in future months he described as provoking a sense of "violation, threat, powerlessness".