Davies v Bridgend County Borough Council

Factual and Procedural Background

The Claimant owns land onto which Japanese knotweed (“JKW”) had encroached from the neighbouring property of the Defendant. Uncontroverted evidence showed that JKW was already present on the Claimant’s land when the property was purchased in 2004. From 2013, the Defendant had, or ought to have had, knowledge of the encroachment and the financial ability to address it, such that fault could be attributed from that date.

The Claimant did not seek an injunction but instead claimed damages for the “residual” diminution in value of the land after treatment of JKW, asserting that stigma persists even when the plant is eradicated. The Court of Appeal awarded £4,900 for that head of loss. The Defendant appealed to the Supreme Court, contending that the damages should be set aside on grounds of factual causation.

Legal Issues Presented

1. Whether, in a private nuisance claim involving a natural hazard for which the Defendant became responsible only from 2013, the residual diminution in value of the Claimant’s land was factually caused by the Defendant’s breach of duty.
2. Whether the standard “but for” test of factual causation applies where the same actionable interference already existed before the Defendant’s breach.

Arguments of the Parties

Defendant's Arguments

• The residual diminution in value existed before 2013; therefore, applying the “but for” test, the Defendant’s breach did not cause the loss.
• Relied on Performance Cars Ltd v Abraham to show that a later wrongdoer is not liable for damage already sustained.

Claimant's Arguments

• The presence of JKW after 2013 constituted an actionable nuisance for which the Defendant should compensate the ongoing loss in value.
• Advanced a secondary submission (ultimately rejected) that earlier treatment would have reduced the residual diminution.

Table of Precedents Cited

Court's Reasoning and Analysis

Judge Stephens (with Judge Burrows concurring) treated the matter as a “pure issue of factual causation.” Because JKW had already encroached before 2013, the alleged damage—stigma causing residual diminution—was present before the Defendant’s fault arose. Applying the orthodox “but for” test, the Court asked whether the residual diminution would have occurred without the Defendant’s breach. The answer was affirmative: the loss existed independently of any post-2013 wrongdoing.

The Court rejected the Claimant’s unpleaded secondary argument that earlier treatment would have reduced stigma, noting the absence of evidence. Adopting the analogy from Performance Cars, the Court concluded that a defendant is not liable when the actionable interference is identical to a pre-existing, non-actionable condition. Accordingly, the Claimant failed to prove a causal link between breach and loss, meaning no tort of private nuisance was established.

Holding and Implications

Appeal ALLOWED; the award of £4,900 in damages is set aside and no damages are payable.

The decision underscores that in private nuisance claims involving natural hazards, liability hinges not merely on the defendant’s fault but also on factual causation. Where the complained-of damage pre-dates the defendant’s actionable conduct, the “but for” test precludes recovery. The ruling does not create new law but reinforces existing principles governing causation and successive events.