Nuisance and the ‘but for’ test

Introduction

Japanese Knotweed (‘JKW’) is bad news for homeowners. Treatment is costly, takes a long time and while it can be managed, it seems that JKW cannot be wholly eradicated.

Davies v Bridgend County Borough Council ([2024] UKSC 15) concerned a claim by Mr. Davies in respect of an encroachment of JKW from the neighbouring land of Bridgend CBC (‘the Council’).

The encroachment began before 2004. The Council became liable in nuisance in 2013 when they knew or ought to have known of the risk of loss or damage to Mr. Davies’ land and failed to take reasonable steps to address that risk.

The nuisance continued until 2018 when the Council implemented a treatment programme.

Mr. Davies brought proceedings in private nuisance in respect of the acknowledged continuing private nuisance between 2013 – 2018.

The claim was for GBP4,900. This was in respect of the stigma in the property market attached to the property because of its having been contaminated by JKW.

The Council’s argument was that this harm was caused when JKW first invaded Mr. Davies’ land. This happened long before the actionable nuisance and so was not caused by the nuisance.

There were, then, three phases:

• 2004 (or earlier) JKW ‘invades’ Mr. Davies’ land from the neighbouring Bridgend land;
• 2013 – this becomes a nuisance when Bridgend either had or were deemed to have the necessary knowledge of the presence of JKW and its harmful effects; and
• 2018 – the nuisance continues until 2018, which is when Bridgend implement an effective treatment programme.

Causation: the ‘but for’ test

The Supreme Court agreed with Bridgend on the causation issue. Mr. Davies’ claim failed because the harm was caused by the invasion of JKW which took place before Bridgend became liable in private nuisance in 2013.

Lord Stephens explained:

‘The standard approach in tort to deciding whether a breach of duty is a factual cause of damage is to apply the “but for” test. This requires one to ask whether the damage would have been suffered but for the breach of duty. If the answer to that question is “no” (ie the damage would not have been suffered but for the breach of duty) the breach of duty was a factual cause of the damage.’ ([80]).

There are exceptional situations where the ‘but for’ test is inappropriate, but this was not one of them ([82]).

Applying the test to the facts of the case, Lord Stephens concluded that:

‘The claimant has not proved that the residual diminution in value would not have been suffered but for the breach of duty. This was because 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.’ ([85]).

Different if things got worse during the period of the continuing nuisance in 2013 – 2018

The outcome might have been different if the harm to Mr. Davies’ land had increased while the nuisance continued:

‘if a claimant can prove that a subsequent breach has increased treatment costs due to the presence of more JKW on the claimant’s land then the additional treatment costs would be recoverable’ ([35], Lord Stephens).

Was Mr. Davies claim one for pure economic loss?

Bridgend contended at first instance and in the Court of Appeal that Mr. Davies’ claim should also fail because damages for the residual diminution in value of his land because of the JKW stigma amounted to pure economic loss.

This argument was rejected by the Court of Appeal in this case. The Court of Appeal held that once the elements of a nuisance claim are present, damages for diminution in value of the claimant’s land would be recoverable.

Neither party challenged this conclusion in the Supreme Court. Nor did the Supreme Court itself criticize it.

Michael Lower

**Disclaimer**: The information provided on the Hong Kong Land Law blog is for educational purposes only. It is intended to offer a general understanding of the cases or issues discussed, not to provide specific legal advice. Readers should not act upon this information without seeking professional legal advice. The views expressed are my own and do not necessarily reflect the official policy or position of any court or legal authority.

Tags: 'but for' test, Causation, Japanese Knotweed, Michael Lower, nuisance, Private nuisance