Japanese Knotweed Litigation

A private nuisance is an activity or a state of affairs existing on land or premises which unduly interferes with the use or enjoyment of neighbouring land.

The claimant/appellant in Bridgend CBC v Davies [2024] UKSC 15 was the owner of a property which adjoined land owned by the defendant local authority. Some time before 2004, Japanese knotweed encroached onto his land from the land of the authority. Neither party was aware (nor could reasonably be expected to be aware) of this until around 2013. The authority did not start any adequate treatment regime of the knotweed on either plot of land until 2018.

In 2019, the claimant/appellant complained that Japanese knotweed was spreading on his property and, when the respondent failed to take such remedial measures as would satisfy him, he issued a claim in nuisance.

Among other heads of claim, he sought £4,900 reflecting the diminution in value of his land which, he said, arose from the “stigma” attached to knotweed by potential purchasers. The authority resisted the claim, inter alia, on the basis that it had only been aware of the knotweed since 2013 and, although it had failed to treat it adequately, any harm which resulted from the knotweed arose from the pre-2004 spread of the plant at which time, because it had been unaware of the knotweed, it could not have been responsible for any nuisance so that any loss which the claimant had suffered was not as a result of its failure to treat the knotweed from 2013 onwards.

The county court found that the authority had been responsible for a private nuisance from 2013-18 as a consequence of its failure to treat the knotweed. It dismissed the claim, however, on the basis that damages for diminution in value were irrecoverable at law. The Court of Appeal allowed an appeal in favour of the claimant, holding both that they were recoverable as a matter of law and that the continuing failure to treat the knotweed between 2013 and 2018 created a private nuisance for which damages should be awarded.

The Supreme Court allowed an appeal in favour of the local authority. The critical issue was not whether damages for diminution in value were recoverable, but, rather, what were the consequence of the finding that the authority had not been aware of the knotweed before 2013? The evidence showed that the knotweed had spread to the claimant’s land well before 2004. Critically, it was no part of the claimant’s case that the inadequate treatment regime in 2013-18 had worsened the knotweed spread. It followed that any diminution in value arose from the 2004 spread, rather than the 2013-18 inadequate treatment regime. The unappealed decision of the county court was that there was no actionable private nuisance in 2004 and it followed that the 2013-18 failures had not caused the diminution in value.

As a matter of general and wider importance, the Supreme Court reiterated the significance of the “but for” test in causation. Would the diminution in value have occurred “but for” the inadequate treatment regime in 2013-18? When framed that way, it was clear that there was no causal link between the breach of duty and the diminution in value.

Oliver Kew

Published on 16/05/2024