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A knotty problem strikes again

The Court of Appeal has recently clarified the basis on which landowners with Japanese knotweed on their land may be liable to adjoining land owners for causing a legal nuisance.

Our article A knotty problem reported a decision in February 2017 by Cardiff County Court to award damages against Network Rail for causing a nuisance to the owners of two residential properties next to land owned by Network Rail on which Japanese knotweed was growing. The court ruled that the presence of Japanese knotweed on Network Rail's land amounted to an unlawful interference with the claimants' quiet enjoyment of their properties, thereby affecting the amenity value. The Court of Appeal has recently rejected Network Rail's appeal against that decision, but for different reasons.

In a separate case, the owners of a residential property were granted an injunction by Truro County Court against a neighbour who allowed Japanese knotweed to encroach onto their land from her land for many years. Although the injunction was issued in November 2017, the court's judgment has only recently been published.

The Network Rail appeal

In Network Rail Infrastructure Ltd v Williams, Network Rail challenged Cardiff County Court's decision to award damages to Mr Williams and Mr Waistell for the diminution in the value of their respective properties and for the cost of a treatment programme to treat Japanese knotweed growing on land owned by Network Rail adjacent to their respective properties. No physical damage was found to have been caused to either of their properties. However, the threat of damage caused by the presence of the Japanese knotweed and the impact it would have had if left untreated were found to have diminished land values.

The court decided this amounted to undue interference with the claimants' enjoyment of their land and was therefore a nuisance.

The Court of Appeal disagreed that a diminution in property values amounted to an undue interference with the enjoyment of land, as it considered that would have extended the scope of nuisance to cover pure economic losses.

Instead, it ruled that the encroachment of the Japanese knotweed rhizomes (underground stems akin to roots) had diminished the claimants' ability to enjoy the amenity and utility of their properties. The Japanese knotweed and its rhizomes did not just carry the risk of future damage to buildings and land, but its presence imposed an immediate burden on the claimants, who faced an increased difficulty in their potential ability to develop their land because of the difficulty and expense of eradicating the Japanese knotweed. That was still a nuisance and the Court of Appeal upheld the decision to award damages to the claimants, amounting to 10% of the value of their respective properties.

The Truro County Court case

In Smith and Smith v Line, Mr and Mrs Smith claimed an injunction against their neighbour, Mrs Line, to force her to take action to deal with the presence of Japanese knotweed on her land. Japanese knotweed from Mrs Line's property had encroached onto their land in the past and they had dealt with those encroachments themselves. But, despite repeated requests, Mrs Line had failed to address the infestation on her land and it once again threatened to encroach on the Smiths' land. The Smiths said that Mrs Line's actions and the presence of the Japanese knotweed had reduced the value of their property. Although they could have claimed damages, they instead sought an injunction compelling Mrs Line to address the problem once and for all.

Mrs Line argued that there had always been Japanese knotweed on both properties, that any encroachment had actually been onto her land from the Smiths' land. Her case was that, in any event, she had taken all reasonable steps to control the Japanese knotweed on her property. However, expert evidence showed seven separate areas of Japanese knotweed on Mrs Line's land, some within a metre of the boundary with the Smiths' land.

Truro County Court ruled that the encroachment of the Japanese knotweed from Mrs Line's land onto the Smiths' land was an undue interference with the Smiths' comfortable and convenient enjoyment of their land. Mrs Line had been aware of the presence of the Japanese knotweed on her land for a long time. The Smiths had successfully eradicated it from their land and Mrs Line's response to the problem had been inadequate. She had known that a management programme with an accredited expert was required, but only chose to pursue it while awaiting the county court's judgment.

Given the risk that Mrs Line would not follow through with the management programme, the county court granted an injunction compelling her to do so.


Both decisions are to be welcomed. They confirm that there is a remedy for those whose land is threatened with the encroachment of Japanese knotweed from neighbouring properties and that, even if there is no actual damage to property, the presence of Japanese knotweed can affect amenity value.

The Truro County Court decision also confirms that in appropriate cases the courts will grant injunctions requiring Japanese knotweed to be properly treated.

Our article A knotty problem contains some practical considerations for owners and occupiers of land with Japanese Knotweed growing on it.

Network Rail Infrastructure Limited v Williams and Waistell [2018] EWCA Civ 1514

Smith and Smith v Line (case number C00TR216), Truro County Court, 6 November 2017


This information is for educational purposes only and does not constitute legal advice. It is recommended that specific professional advice is sought before acting on any of the information given. © Shoosmiths LLP 2022.


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