A recent Court of Appeal decision provides a further warning for landowners and developers about the liability exposure to adjoining owners for the migration of harmful things from their land to adjoining property. The case happened to concern the invasive species Japanese knotweed, but the general principles reiterated by the Court  are also capable of applying to other forms of migratory contamination, and demonstrate a wide concept of ‘damage’

In the case of Network Rail Infrastructure Ltd v Williams [2018] EWCA Civ. 1514, 3rdJuly 2018, the Court of Appeal ruled that the encroachment of Japanese knotweed from one property onto a neighbouring property was capable of giving rise to a claim in private nuisance despite the fact that no physical damage had yet been caused. The Court ruled that the mere riskof future physical damage imposed an immediate burden on the claiming adjoining landowners on account of the increased difficulty of developing their land as a result, and therefore diminished the utility and amenity of their property. They were awarded damages for residual diminution in the market value of their property as a result of the encroachment of the knotweed.

The case is of wider significance however. The Court of Appeal reminded us of some general principles which can apply not only to invasive species but other forms of ‘interference’ such as migrating contamination. These general legal principles are: (a) a private nuisance is a violation of property rights involving either an interference with the legal rights of a landowner, including a legal interest in land, or interference with the amenity of the land; (b) the categories of nuisance (encroachment, interference and physical injury) were merely examples of violations of property rights, and such rigid categorisation did not easily accommodate examples of nuisance in new social conditions; (c) the proposition that damage was always an essential requirement of the cause of action was not entirely correct: the concept of damage in this context was “elastic”, it being well-established that, in the case of nuisance through interference with the amenity of land, physical damage was not necessary; and (d) nuisance could be caused by inaction or omission as well as by positive activity.