The presence of Japanese knotweed could result in nuisance claims from adjoining landowners, the Court of Appeal has confirmed.

The case of Network Rail Infrastructure Limited v Stephen Williams and Robin Waistell concerned the encroachment of Japanese knotweed, which was present on Network Rail's adjoining land, onto their properties. The Recorder, in giving judgment for the claimants, had concluded that the presence of knotweed on Network Rail's land within seven metres of the claimants' properties was an actionable nuisance simply because it diminished the market value of the claimants' respective properties, owing to lender caution in such situations.

The Court of Appeal thought this was wrong in principle and criticised the Recorder's ruling for extending the tort of nuisance to a claim for pure economic loss. The purpose of the tort of nuisance, Sir Terence Etherton MR said, is to protect the owner of land in its use an enjoyment of the land; its purpose is "not to protect the value of property as an investment or a financial asset."

However, as the presence of the Japanese knotweed had diminished the homeowners' ability to enjoy the amenity and utility of their properties, they were entitled to damages.

What does this mean for landowners?

Japanese knotweed is notoriously difficult to eradicate. It is already subject to a strict regime of control under the Wildlife and Countryside Act 1982 (as amended by the Infrastructure Act 2015). The possibility that landowners could also find themselves on the other end of a claim for private nuisance should be a further incentive for landowners to take action and not ignore the weed.

Landowners selling their properties must ensure that they provide accurate replies to enquiries. It is likely that, as result of this case, buyers will be more alert to potential issues with knotweed.