Property owners who find Japanese knotweed growing nearby or on their land should be aware of the very serious problems it can cause. Schedule 9 to the Wildlife and Countryside Act 1981 [WCA 1981] lists certain plants that have become established in the wild in Great Britain but which the law seeks to prevent spreading further. This includes Japanese knotweed which is categorised as an Invasive Non-Native Species, otherwise referred to as an INNS.

Japanese knotweed can grow at the rate of 10cm a day during the summer. It is extremely difficult to eradicate and can make property unsaleable. To make matters worse, research indicates that very few people are readily able to identify Japanese knotweed. Property owners therefore need to be alive to the risks that it can create.

The presence of Japanese knotweed can give rise to common law nuisance where it involves an unlawful interference with the use and enjoyment of another's land and results in loss of enjoyment and property damage. Added to this will be the cost of eradication and potential ongoing liability for re-infestation.

The usual principles of common law nuisance apply so the nuisance must be substantial or unreasonable and could arise from either a single incident or a state of affairs. This aspect of common law nuisance is a developing area but it is uncertain whether such action amounts to a statutory nuisance under Part 3 of the Environmental Protection Act 1990 [EPA 1990] which requires physical damage.

Japanese knotweed can also give rise to criminal penalties. The WCA 1982 creates various offences including making a person guilty of an offence if they plant or otherwise cause to grow an INNS. Any person found guilty of an offence can on summary conviction in a magistrates’ court be committed to six months imprisonment and/or an unlimited fine. On conviction on an indictment a property owner can be committed to two years imprisonment, a fine or both.

It is important to note that a failure to take reasonable measures to confine an INNS that results in it spreading could amount to causing an INNS to grow in the wild and consequently give rise to an offence.

Negligent or reckless behaviour such as inappropriate disposal of garden waste resulting in an INNS becoming established in the wild also constitutes an offence giving rise to similar potential liabilities.

Depositing controlled waste such as Japanese knotweed is likely to be a breach of Section 33 of the EPA 1990. Similar offences arise under Regulation 52 of Habitats Regulations 2010 in respect of disposals from ships!

Added to this, local authorities have enforcement powers to require clearance of knotweed under Section 215 of the Town & Country Planning Act 1990 and any failure to comply can lead to prosecution, a fine and remedial costs.

A community protection notice under the Anti-social Behaviour, Crime and Policing Act 2014 also contains powers which might be used against an occupier failing to clear knotweed.

If therefore an owner or occupier of land fails to control Japanese knotweed or allows it to spread onto neighbouring land this may give rise to costly claims for loss of enjoyment or amenity, the cost of removal and any potential costs to prevent a re-infestation and potential criminal sanctions.

In the recent Court of Appeal decision in the case of Network Rail Infrastructure Limited v Williams and Another [2018] EWCA on 3 July 2018, the Court of Appeal confirmed that it is not possible for there to be an actionable nuisance for diminution in value caused by the presence of Japanese knotweed, as this would be an action for pure economic loss which cannot be claimed in nuisance.

However, the Court of Appeal held that the mere presence of Japanese knotweed can still be an actionable nuisance even before it causes physical damage to neighbouring land. This is likely to be of particular concern to land owners of public land, railways, roads and rivers and the like which may have Japanese knotweed on their property near boundaries with neighbours.

Standard residential enquiries ask about the presence of Japanese knotweed and every CQS lawyer must use the standard property information form TA6. Sellers need to be very careful how to respond. A seller who does not occupy and who has not inspected the property may well reply that the buyer should rely on his or her own inspection and survey. However, if the seller replies not so far as the seller is aware without making reasonable efforts to check for the presence of Japanese knotwood, the seller risks being found liable for misrepresentation.

It is not unusual that even where a seller has had the plant destroyed and the ground treated, for the buyer still to withdraw from a purchase where he or she may not be satisfied with the guarantee provided by the company treating the land. Unfortunately there is no industry standard policy and most are issued without any underlying insurance so buyers are relying upon the treatment company staying in business to honour their guarantee.

In recognition of the importance of the issue to lenders, The Council of Mortgage Lenders has stated that mortgage lenders will expect the presence of knotweed to be noted on residential valuation reports.

Where does this leave us? The Court of Appeal’s decision in the recent NetworkRail case is therefore interesting for its clarification of the law of nuisance.

The conclusion reached by the Court of Appeal is that the proposition that damage is always an essential requirement of the cause of action is not entirely correct. The concept of damage in this context was considered to be very broad. In the case of nuisance through the interference with the amenity of land, physical damage is not necessary to complete the cause of action.

Nuisance can also be caused by inaction or omission as well as by positive activity. An occupier will be liable for failing to act reasonably to remove the Japanese knotweed after becoming aware of it and where it was foreseeable that it would damage a neighbour’s land.

A property owner is likely therefore to be granted an injunction requiring a neighbour to control knotweed on his or her land on the basis of anticipatory damage. An injured owner will not, however, recover damages for loss of value (pure economic loss) but will recover damages for loss of amenity.

Does the recent Court of Appeal decision also have wider implications?

Where property owners can show possible damage, will this be sufficient for instance to try to prevent fracking operations on neighbouring land?