Davies v Bridgend County Borough Council – Japanese Knotweed Update 2024

On 8th May 2024 the Supreme Court unanimously overturned last year’s Court of Appeal decision in Davies v Bridgend County Borough Council.

In doing so, it has clarified the basis on which diminution in value may or may not be awarded in Japanese Knotweed claims. In short, diminution in value which has already occurred prior to the defendant’s breach will not form part of any award.

Mr Davies brought a claim for nuisance against the council arising from the encroachment of Japanese Knotweed onto his land. It was not disputed that at some date well before Mr Davies purchased the land, in 2004, the Knotweed had already spread onto it from the council’s land. In 2004, encroachment of Japanese Knotweed was not an actionable private nuisance. That arose in 2012 when the council became, or ought to have become aware, of the risk of damage and loss of amenity to Mr Davies’ land due to official guidance published by RICS at that time. The law allows for a reasonable period of time to abate a nuisance, but by 2013 the council had failed to implement a reasonable and effective treatment programme to control the Knotweed and prevent ongoing encroachment. At this point, the court accepted that the council was in breach of its duty of care to neighbouring landowners, including Mr Davies. It was not until 2018 that the council effected such a programme.

The Court of Appeal upheld the first instance finding that the council was in continuing breach between 2013 and 2018, and that damages for the residual diminution of the value of Mr Davies’ land were recoverable. This was notwithstanding that the Knotweed had spread onto Mr Davies’ land long before the council could reasonably have been expected to be aware of the risk presented. In effect, the Court of Appeal took the view that as the council had subsequently breached its duty of care in 2013, and that state of affairs continued until 2018, it would be liable for the residual diminution in value which had occurred prior to the breach arising. 

From a “black letter law” perspective, this decision was somewhat problematic; if the breach was not causative of the loss, how could it be correct that damages could be awarded? It also proved problematic from a practical perspective, and we commented on the concerning fallout in an Insights article last year (Japanese knotweed: 2023 update). The judgment heralded a revival of previously rebuffed claims, many of which we had challenged on the basis that losses which had already occurred before a breach arose could not be recoverable (without the diminution in value head of loss, the majority of claims fell below the small claims track value limit and were therefore unappealing for claimant solicitors to pursue.)

In overturning the Court of Appeal’s decision, Lord Stephens, giving the leading judgment, set out the key statement on which the decision hinged: 

“If the diminution in value would have occurred in any event, then the defendant’s breach of duty is eliminated as a cause of the diminution in value so that there would be no causal link between the defendant’s breach of duty and the diminution in value.”

Lord Burrows clarified further: 

“The JKW was already present on the claimant’s land before 2013 so that the residual diminution in value had already been brought about by the natural, non-actionable, encroachment of the JKW … the claimant has failed to prove that the alleged damage (or, put another way, the alleged undue interference with the claimant’s use and enjoyment of land) was factually caused by the breach of duty which was committed from 2013.”

The court was not presented with any evidence that the council’s breach of duty between 2013 and 2018 had increased or materially contributed to the diminution in value of Mr Davies’ land. Indeed, the encroachment, and resultant diminution, had occurred long before any breach by the council. The council’s subsequent breach was therefore of no consequence and could be eliminated as a causative factor. 

Mr Davies sought to rely upon Delaware Mansions Ltd v Westminster City Council [2001] UKHL 55, which established that where there is a continuing nuisance which commenced prior to the claimant’s ownership of the affected land, the claimant is entitled to claim for the abatement of the nuisance and to recover the reasonable costs of doing so. The same reasoning could not be applied to this case because a loss representing a diminution in market value is not an aspect of reasonable costs incurred in abating a continuing nuisance. Further, the critical legal point established by Delaware was that a change in ownership of the land did not prevent the current owner from claiming for nuisance which had commenced pre-ownership, provided that the state of affairs continued. Delaware is not authority for the proposition that diminution in market value (or indeed any other loss) is recoverable, if it occurred prior to a defendant’s breach of duty.  In short, a claimant cannot claim for pre-breach losses retrospectively.

The judgment has left us with some unanswered questions. The court did not explicitly say that a claimant must prove that the diminution in value must also result from a breach within the limitation period. We had hoped this would be covered, not least as the Davies proceedings were commenced in 2020, with limitation therefore reaching back to 2014 rather than the start of the breach in 2013. It is hoped that this was left unsaid simply because the court did not need to comment on it as no diminution award was made. However, it seems to be logical and implicit that pre-limitation losses are similarly not recoverable; such a position would align with the substantive finding. There will also be instances where the evidence establishes that diminution in value has been caused prior to encroachment simply from the presence of nearby Knotweed. This point has not been specifically addressed in case law but again, we consider that this would fail the test for causation by physical encroachment, established in Williams and Waistell v Network Rail EWCA Civ 1514.

It will be interesting to see how claimant firms react in cases where the Knotweed encroachments occurred more than six years previously and/or before the defendant was in breach of its duties. A claimant would now have to plead, and support with expert evidence, that additional or separate diminution in value was caused after the initial encroachment by a delay in the defendant treating the Knotweed. Surely it will be a brave claimant who would be willing to pursue such a head of loss. 

Overall though, this is a far-reaching and positive decision for us and our clients. By correctly applying the standard “but for” test, the Supreme Court instantly recognised the council’s breach of duty to be an “irrelevant causative factor” when applied to the facts. Whilst the Court of Appeal had rejected the “attractive simplicity” of the Council’s argument on causation, the Supreme Court considered it perfectly correct and applicable. The judgment has brought welcome clarity to a number of hitherto uncertain cases, and we anticipate that claimant appetite for litigation in this arena will be notably tempered going forwards.