What is the test for liability in nuisance cases?

In 1926, Rowlatt J. in Noble v. Harrison, [1926] 2 K.B. 332, in what might be considered obiter comment, envisaged how a situation could arise which would result in an action for nuisance succeeding on the basis of the application of the principle of strict liability; that is to say, in a situation where the defendant, who did not create a nuisance in the first instance and did not by neglect of duty allow it to arise, neither had knowledge of the existence of the danger nor means available whereby the existence of the danger could be ascertained. The issue in that case revolved around a branch of a tree, growing on the defendant’s land, which overhung a highway at a height of 30 feet. In fine weather, the branch suddenly broke, fell upon the plaintiff’s vehicle, which was passing along the highway, and damaged it. At trial it was found that neither the defendant nor his servants knew that the branch was dangerous and it was further found that the fracture resulted from a latent defect not discoverable by any reasonably careful inspection but, nevertheless, the plaintiff succeeded in an action for nuisance. On appeal it was held that a branch overhanging a highway does not constitute a nuisance if it is at such a height as not to obstruct free passage and the decision of the court was that the finding of liability in nuisance could not stand and the appeal thus succeeded.