In March 2023, we reported on a Court of Appeal case which had confirmed that a landowner was able to claim damages for the diminution in value to their property caused by Japanese Knotweed on neighbouring land.

The case was appealed to the Supreme Court and arguments were heard in February 2024, with the Supreme Court releasing its judgment on 7 May 2024.

The Supreme Court has now overturned the Court of Appeal’s decision.

Initial proceedings

Japanese Knotweed is a destructive and invasive plant which spreads quickly and can cause physical damage to buildings if not treated or contained. It spreads via its large underground network of roots, or rhizomes.

In 2004, the Claimant, Mr Davies, purchased a property which backed onto railway sidings. In 2017, he discovered the presence of Japanese Knotweed on his property, which had spread from a neighbouring property, owned by Bridgend County Borough Council.

It was agreed that the council had been aware of the presence of the Japanese Knotweed since around 2013, but did not take steps to treat it until around 2018.

Mr Davies initially issued proceedings for nuisance and part of his claims were rejected as the Japanese Knotweed had not actually caused any physical damage to his property and he could not claim for “pure economic loss”.

Mr Davies argued, however, that the stigma of there being Japanese Knotweed on a neighbouring property (even if it had been treated) reduced the value of his property, for which he should be awarded damages.

Court of Appeal awards for value diminution

The Court of Appeal stated that in cases where Japanese Knotweed was present on a neighbouring property, there was no nuisance if there was no evidence that the Japanese Knotweed had encroached upon next door or where the encroachment had been trivial.

However, in Mr Davies’ case, there was evidence that the rhizomes had encroached onto his land and such encroachment was not trivial. In such circumstances, this amounted to a physical interference with Mr Davies’ property and, as such, consequential losses, including diminution in value were recoverable.

The council argued, amongst other things, that as the rhizomes had been present before 2004 when Mr Davies purchased his property, they should not be responsible for any loss which was suffered before their breach (of failing to treat the knotweed between 2013 and 2018) as such loss cannot have been caused by their breach. The Court however rejected this argument and said that the nuisance was a continuing one and that the harm to Mr Davies’ quiet enjoyment of his land persisted.

Mr Davies was awarded the relatively low sum of £4,900 for the diminution in value to his property. However, it was estimated that legal costs ran into hundreds of thousands of pounds, which was presumably one of the reasons why the council decided to appeal the decision to the Supreme Court.

The Supreme Court turns tables

The council’s appeal was based on one narrow point, namely whether the diminution in value in Mr Davies’ land was caused by the council’s breach of duty. The council argued that if loss precedes the breach of duty, then such breach cannot have caused the loss. In Mr Davies’ case, they argued that the loss (i.e. the diminution in value of his land) had already occurred prior to the council’s breach (i.e. their failure to treat the Japanese Knotweed between 2013 and 2018).

Mr Davies did not raise any counterarguments, simply relying on the decision of the Court of Appeal.

The Supreme Court decided in the council’s favour. It was not in issue that the Japanese Knotweed had been present on Mr Davies’ land since before 2004 and the diminution in value to his land had therefore taken place before then and long before 2013 when the council had first breached their duty in not treating the Japanese Knotweed.

Accordingly, they allowed the appeal and did not award any damages to Mr Davies, who will in turn now have to pay the council’s legal costs.

Clarity in cases involving Japanese Knotweed

The decision provides some clarity in cases involving Japanese Knotweed. Whilst each case will turn on its own specific facts, councils may be able to defend such claims if they can prove that the Japanese Knotweed was present on claimants’ land long before their duty to treat the Japanese Knotweed occurred.