Nuisance by Knotweed – Jeremy Hyam QC

25 July 2018 by

japanese-knotweed-1.jpgA radical problem determined by ‘straightforward application of established principles’? 

 Network Rail Infrastructure v. Stephen Williams (1) Robin Waistell (2) [2018] EWCA Civ 1514 – read judgment


Hancock’s curse, monkey fungus, elephant ears, pea shooters, donkey rhubarb are all (bizarre) English names for Fallopia japonica or Japanese knotweed.  Although initially lauded for its beauty (it was so celebrated that in 1847 it was named by one Horticultural society as the ‘most interesting new ornamental plant of the year’) it is now well known as a fast growing and pernicious weed that is very difficult to eradicate. This is because it has a large underground network of roots (rhizomes). So bad is its destructive nature that since 2013 a seller of property is required to state whether Japanese knotweed is present on their property through a TA6 form – the property information form used for conveyancing.

Its destructive potential, and its potential for devaluation of property was at the heart of this recent decision of the Court of Appeal.

The appeal arose from the decision of Recorder Grubb sitting in Cardiff that the Appellant, Network Rail (‘NR’), was liable in nuisance by reason of the devaluation of the Claimant’s property due to the presence of knotweed on an embankment behind the Claimant’s property. The appeal raised a number of key issues as to what kinds of damage give rise to an actionable claim in the tort of private nuisance.


The Claimants were the owners of two bungalows near backing onto a railway embankment in Maesteg, in Wales and separated only by an access path owned by Network Rail. A large amount of Japanese Knotweed grew on the embankment and had done so for some 50 years.

The Claimants put their claim in two ways: nuisance by way of encroachment, and nuisance by way of breach of quiet enjoyment of amenity of property. The Recorder addressed each in turn.

First, in respect of encroachment, he identified the claim as ‘an action on the case’ the gist of which was ‘actual damage’. Although he found there had been encroachment of the roots of the knotweed onto both properties he rejected the encroachment claim on the ground that the encroachment had caused no actual (physical) damage to property.   He also held that the fact that the presence of the Japanese knotweed had resulted in a diminution in the value of the claimants’ properties did not constitute damage. ‘Risk of damage’ was not enough.

Second, as to quiet enjoyment/loss of amenity, he held that the presence of Japanese knotweed on NR’s land in close proximity to the boundary of the Claimants’ respective properties was a sufficiently serious interference with the quiet enjoyment or amenity value of their properties as to constitute an actionable nuisance – it was an unreasonable interference with their enjoyment of their respective properties as its presence affected their ability to sell their properties at a proper market value. This was, he reasoned, because the claimed nuisance produced a blight upon the property that left the property owner in the position of the uncertainty that his or her property may, no longer, be the valuable asset and home that it was thought to be.  Essentially, he held Claimant’s had a valid claim loss of amenity that loss being the pure ‘economic loss’ of the ‘blight’.

Appeal to the Court of Appeal

NR unsurprisingly appealed.  Put simply, they argued that absent actual damage there was no claim in nuisance. Economic loss was not a kind of damage which was recognised in the tort of nuisance, which is quintessentially, a property based tort.

The Court of Appeal agreed.  They held that the Recorder’s conclusion that the presence of knotweed on NR’s land within seven metres of the claimants’ properties was an actionable nuisance simply because it diminished the market value of the claimants’ respective properties was wrong in principle. The purpose of the tort of nuisance is not to protect the value of property as an investment or a financial asset. Its purpose is to protect the owner of land (or a person entitled to exclusive possession) in their use and enjoyment of the land as such as a facet of the right of ownership or right to exclusive possession. The decision of the Recorder wrongly extended the tort of nuisance to a claim for pure economic loss. The Recorder’s decision was not incremental development of the common law by analogy but rather a radical reformulation of the purpose and scope of the tort.

But – and there was always going to be a but – the Court of Appeal upheld the Recorder’s decision on grounds not advanced before the Recorder, namely that the Recorder was wrong to reject the claim in nuisance (loss of amenity) based on the spread of the knotweed roots on to the claimants’ respective properties from NR’s land. The Court of Appeal acknowledged Lord Lloyd’s threefold categorisation of nuisance from Hunter v Canary Wharf, namely:

(1) nuisance by encroachment on a neighbour’s land,

(2) nuisance by direct physical injury to a neighbour’s land; and

(3) nuisance by interference with a neighbour’s quiet enjoyment of his land,

but explained that the difficulty with any rigid categorisation is that it may not easily accommodate possible examples of nuisance in new social conditions or may undermine a proper analysis of factual situations which have aspects of more than one category but do not fall squarely within any one category, having regard to existing case law.

The Court of Appeal expressly doubted the proposition that actual damage is a prerequisite of the cause of action for nuisance because nuisance is derived from the old form of ‘action on the case’ and said it must be treated with considerable caution. The proposition is not entirely correct they said, and in any event, the concept of damage in this context is a highly elastic one.

So what is relevant damage in this case?

What is “relevant” said the Court of Appeal is

the objective effect on the amenity value of the land itself, and it is that effect which satisfies any requirement there may be to show damage.

Provided, by reference to all the circumstances of the case and the character of the locality, and according to the objective standards of the average person, the interference with amenity is sufficiently serious, there will be an actionable private nuisance. Here there was a nuisance because the mere presence of the rhizomes imposed

an immediate burden on the owner of the land in terms of an increased difficulty in the ability to develop, and in the cost of developing the lands, should the owner wish to do so.

Since the rhizomes ‘affect the owner’s ability fully to use and enjoy the land’ they are, said the Court of Appeal a ‘classic example’ of an interference with the amenity value of the land.


The judgment will have profound consequences for the very large number of households affected by the presence of Japanese Knotweed from neighbouring property. Particularly those who, like the Claimants live near railway embankments where Japanese knotweed is often to be found.  The simple point is that roots under the Claimant’s land may be enough to constitute actual damage for the purposes of ‘loss of amenity’ even without physical damage to property.

For good measure the Court of Appeal has added that, in appropriate circumstances, a claimant should be able to obtain a final mandatory injunction where the amenity value of the land is diminished by the presence of roots even though there has not yet been any physical damage.  That injunction may require the expensive and time consuming eradication of the root system from the Claimant’s land.


Although the Court of Appeal explained that their decision was ultimately determined from ‘a straightforward application of established principles of property law’, the blurring of the categories in Hunter and the doubting of the requirement for ‘actual damage’ is really anything but.  Definition of loss of amenity as loss of development potential sounds to this layman a lot like ‘economic loss’.

David Hart Q.C and Jessica Elliott, both of 1 Crown Office Row, acted for Network Rail. They were instructed by BLM.










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