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Loss Of Amenity From The Presence Of Japanese Knotweed – The Final Final Word In Davies V Bridgend County Borough Council (2024)

Last year we reported on this case about whether a home owner could claim for ‘residual diminution in value’ from the encroachment of Japanese knotweed (JKW) from neighbouring land.

We thought that the Court of Appeal had given the final word in Mr Davies’ favour. However, the matter was appealed to the Supreme Court who handed down their judgment in May 2024.

The Law on Nuisance

It is useful to remind ourselves that private nuisance is violation of real property rights from either

a) Physical damage to land,
b) Encroachment
c) Interference with the amenity of the land (right to use and enjoy)

The Facts

Mr Davies had owned a property at 10 Dinam Street, Nant-y-moel, Bridgend, Wales since 2004. His property was next to land owned by Bridgend County Borough Council (BCBC).

The JKW had probably been present in BCBC’s land for over 50 years, well before 2004.

Mr Davies started to have concerns in 2017 about the JKW which was spreading from the neighbouring land into his. He complained about this to BCBC in 2019, who had started treating the JKW from 2018.

The Previous Decisions

Mr Davies issued proceedings in 2020 for nuisance against BCBC for a sum of £4,900 being the amount representing a residual diminution in value of the property – the ‘blight’ even after the JKW had been treated.

It was not challenged that BCBC knew or ought to have known about the risk of damages and loss of amenity to Mr Davies’ land as a result of publicly known information about JKW at that time. Therefore there was a continuing duty between 2013 and 20218.

Mr Davies relied on the evidence of Mr David Raine a chartered surveyor and valuer who concluded the presence of JKW adversely affected the value of the property as a result of the stigma attached to JKW in the current property market.

However despite the breach, the judge in the first instance decided in 2021 that Mr Davies could not claim for the loss in amenity.

Mr Davies appealed.

The first appeal was dismissed in May 2022.

Mr Davies appealed again and the case was heard in the Court of Appeal in 2023 who found for Mr Davies.

They held that as there was a continuing breach (a non-trivial physical encroachment) between 2013 and 2018; the harm remained in 2018 and was therefore caused by the continuing breach.

BCBC appealed and the matter was heard by the Supreme Court in February 2024.

The Supreme Court Decision

The issue that the Supreme Court were called upon to decide was whether the residual diminution in value was caused by the defendant’s breach of duty in private nuisance

The court confirmed that the relevant test is the “but for” test which asks:

would the diminution in value of which the claimant complains have occurred “but for” the breach of duty of the defendant between 2013 and 2018? 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, as a matter of factual causation, between the defendant’s breach of duty and the diminution in value.

They concluded that

  • the diminution in value had occurred long before any breach by BCBC
  • the application of the “but for” test in this case eliminates the subsequent breach of duty as a causative factor
  • the diminution in value would have occurred in any event
  • there is no causal link between BCBC’s breach of duty and the diminution in value claimed

The appeal was therefore dismissed


This has now limited the liability for landowners – any losses claimed has to be actually caused by their breach of duty (and not before) – timing is therefore crucial

However, they should not be complacent and must take reasonable steps to treat JKW they ought to have known about.

It is widely accepted that since 2012 and publication of the RICS report on “Japanese Knotweed and residential property”, there was constructive knowledge of the risks from JKW.

Although this report has now been supersede by the 2022 version which seeks to address public concerns and misunderstanding about JKW

Although this case was only worth £5,000, its importance cannot be overlooked – it required 3 appeals, and the intervention of Network Rail Infrastructure Limited, who own and manage land on which there is widespread growth of JKW.

It is imperative to have appropriate insurance, advice and treatment when dealing with Japanese Knotweed. If you would like to discuss this in more depth, contact our leading Property Dispute solicitors now on 0330 822 3451 or request a call back.


Further Reading