30 08 2017 Insights Litigation & Dispute Resolution

Landmark court ruling for failure to control the spread of Japanese knotweed

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By Lisa Mansfield
25 April, 2017

In this landmark case, a Cardiff Court has found Network Rail responsible for an actionable nuisance for failing to take steps to prevent Japanese knotweed from blighting properties lying close to its railway embankment. We take a look at the case, its possible repercussions and whether this line of reasoning is likely to be followed in Ireland.

Japanese knotweed – what is it?

Before diving into the facts of the case, for those unfamiliar with the plant, Japanese knotweed is a bamboo like plant that was brought to Europe from Japan in the mid-19th century.

Initially lauded for its beauty and potential as animal feed, it has spread across the islands of Ireland and Great Britain, particularly along watercourses, transport routes and waste grounds where its movement is unrestricted. Without the pests and diseases that control it in Japan, it grows and spreads rapidly in “non-native” Europe, displacing native flora and more importantly from a liability point of view, causing significant structural damage.

It’s also particularly virulent and hard to kill. It can propagate from only a small clipping and can take years to eradicate with chemicals. The cost to the London Olympics to remove Japanese knotweed from the 10 acre Olympic site was more than £70 million1 and it’s estimated to be causing £166 million (€231 million) in damage annually in Britain.

The Facts of the Case2

The claimants owned neighbouring semi-detached bungalows in South Wales, whose rear walls abutted an access path owned by the defendant. The path led to an embankment, also owned by the defendant, on which a large growth of Japanese knotweed had been present for at least 50 years. The defendant had been aware of the Japanese knotweed in the locality since 2008 as part of its track inspection regime and had been controlling the weeds so far as required to maintain visibility on the line.

Both claimants asserted that the defendant was liable for the knotweeds encroachment upon their land. Secondly, they claimed that the presence of the knotweed on the defendant's land was an interference with the quiet enjoyment or amenity value of their properties as it affected their ability to sell their properties at market value.

While the claimants failed to prove their case on their first ground due to a lack of evidence of damage to the bungalows due to the encroachment, the Court did find in favour of the claimants on their second ground. It found that the presence of the knotweed had devalued the claimants’ property and even if treatment took place, their saleable values would still be below the market value. Even though there was no physical damage and no effect on the utility of the land, the Court found that the amenity value of a property is not simply the use and enjoyment of the land, but can include the ability to dispose of it at a proper value. He rejected this as being equivalent to pure economic loss. The Court also found that the defendant had constructive knowledge of the risk of knotweed spreading to neighbouring properties following the publication of materials by the Royal Institute of Chartered Surveyors and the Property Care Association in 2012. Further, since that time the defendant had failed to carry out its obligation as a reasonable landowner to eliminate the knotweed problem and prevent the relevant interference with the quiet enjoyment of the claimants' land.

The claimants were awarded £15,000 in damages to cover the cost of treatment of the knotweed and the residual diminution of the value of their properties.


The judgment has serious ramifications for landowners. It puts an onus on property owners to control and remediate any issue, particularly near houses, as soon as they come to light. This will be of particular importance to those responsible for tracts of public land as in 2015, UK ministers accepted a national eradication programme for Japanese knotweed would be prohibitively expensive at £1.5 billion. Thus, we are going to see more and more homeowners having to take to the courts in order to protect their properties.


Japanese knotweed is a regulated species in Ireland and under Regulation 49(2) of the European Communities (Birds and Natural Habitats) Regulations, 2011 (S.I. No.477 of 2011), “any person who plants, disperses, allows or causes to disperse, spreads or otherwise causes to grow,” Japanese knotweed shall be guilty of an offence.

This places an onus on a landowner to be responsible to ensure that they are not causing or allowing knotweed to be dispersed or spread. However, due to knotweed’s durability and the ease with which it can be spread, it will be interesting to know where authorities will draw a line in this regard. Will ignoring a colony of knotweed on your property (as many public authorities around the country are continuing to do) be enough to ground such an offence?

As regards civil liability it is unknown whether Ireland will follow England and Wales in allowing a cause of action in nuisance where a person fails to keep Japanese knotweed present on their property under control and where no damage to the neighbouring property structure can be proved. However, following the decision in Glencar3, where the Supreme Court sought to make it far harder to establish a duty of care in new situations not clearly governed by precedent, it appears that there will be a high hurdle for Irish litigants to jump in order to distinguish such a case from one of pure economic loss.

For more information on the content of this Insight contact:
Lisa Mansfield, Associate Solicitor, lisa.mansfield@rdj.ie, +353 21 4802731

1 For an in-depth look at the lengths the London Olympic Committee had to go to clear the knotweed colonisation see their report - http://learninglegacy.independent.gov.uk/documents/pdfs/design-and-engineering-innovation/13-japanese-knotweed-dei.pdf
2 Waistell and Williams v Network Rail Infrastructure Limited, Unreported, County Court (Cardiff), 2 February 2017.
3 Glencar Explorations v Mayo County Council (No. 2) [2002] 1 IR 84
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