Landowners should sit up and take notice of the Court of Appeal's ground-breaking decision to award thousands of pounds in compensation to a property investor, the value of whose land was blighted by notoriously invasive Japanese knotweed.

The case concerned an investment property that adjoined local authority-owned land on which the pernicious weed had apparently been growing for over 50 years. Its owner sought damages from the council on the basis that the plant's relentless encroachment onto his land amounted to a nuisance.

Following two hearings, the owner succeeded in establishing that he had suffered a nuisance for a period of five years prior to the council taking steps to eradicate the weed from its land. However, he was refused compensation in respect of the blight on the value of his land arising from the infestation. His loss in that regard was found to be purely economic and thus irrecoverable.

Upholding his appeal against that outcome, the Court noted that the case raised an important point of principle. It found that, in nuisance cases, there is no legal bar on the recovery of damages to reflect pure economic loss. The owner's loss arising from the diminution in the value of his land was not, in any event, purely economic because of the physical manner in which it had been caused.

Japanese knotweed's evil reputation is such that the residual blight on the value of his property continued even after it was eradicated. The nuisance arose because of the plant's physical encroachment onto his property, interfering with his amenity and quiet enjoyment of his land. The blight was a consequence of that nuisance and he was thus entitled to be compensated in respect of the damage to his economic interests.

The council argued that the encroachment was historical and that any diminution in the value of the owner's land arose long before any nuisance was established. The Court, however, found that the council's delay in treating the infestation gave rise to a continuing loss for the owner. Until the council treated the Japanese knotweed on its land, any attempt by the owner to eradicate it from his own property would have been futile. In awarding him £4,900 in damages, the Court found that that was a reasonable sum to reflect the diminution in his property's value.