D permitted travellers to live on its land which adjoined P’s farm. With D’s knowledge they often trespassed, stole and harmed P’s sheep. P sued D for nuisance. CA reused to strike out P’s claim and remitted it for trial. It held that the owner-occupier of land could be liable in nuisance for the unlawful activities of his licensees or persons based on his land which took place off his land, where such nuisance consisted of repeated acts committed on the victim's land, to the owner-occupier's knowledge, and which interfered with the victim's use and enjoyment of his land.
Evans LJ: What is required, per Lord Goff/Lloyd in Hunter (concerning whether a tall building was capable of constituting interference) is some form of “emanation”, and there is no reason why this “emanation” could not be the travellers themselves.
It seems very artificial to describe thieves as an “emanation” in the same light as a seepage of chemicals or noise or smell, since it is not the people but their subsequent actions that cause the harm. However it seems a fair conclusion since the council knew of the problems but failed to take action, which is tantamount to authorisation.