Williams v Network Rail Infrastructure Ltd; Waistell v Network Rail Infrastructure Ltd was determined in Cardiff County Court 2 February 2017.

The two claimants (Williams & Waistell) were the respective freehold owners of two adjoining properties in South Wales. The defendant owned land to the rear of these properties upon which Japanese Knotweed, a pernicious weed with the capability to spread underground through its roots and rhizomes, had been identified.

The claimants brought claims against the defendant in private nuisance, claiming that the knotweed had encroached on their land and as such had unreasonably interfered with their quiet enjoyment or amenity of their properties, since its presence affected their ability to sell at full market value.

A claim in private nuisance could not be successful if no actual damage had been suffered. In this case although it was agreed that the knotweed had encroached onto the claimants properties there was no evidence of any physical damage to either the properties or to the load bearing soil beneath. The encroachment claims therefore failed.

With regards to the claim based on unlawful interference with quiet enjoyment or amenity, the court determined that liability only arises if the defendant knew, or ought reasonably to have known, of the state of affairs giving rise to the nuisance. Once aware of the risk the defendant was under a duty to do all that was reasonable to prevent or minimise that risk.

The amenity value of a property was determined to include the right to expect that one’s property could be sold at full market value. Any interference in this assumption should be regarded as a legal nuisance.

The court determined from the evidence that the defendant ought to have known by 2012 of the risk of damage and loss of amenity to the claimants’ properties caused by the proximity of the knotweed. As a result of its failure to address the knotweed until 2013, and its inadequate treatment thereafter, the defendant had failed to fulfil its obligation as a reasonable landowner to eliminate and prevent the interference with the claimants’ quiet enjoyment of their land.

Held: the claims were allowed