One of the homeowners at the centre of a Court of Appeal case over "pernicious" Japanese knotweed has said his fight for compensation is "not over".
Stephen Williams, of Lwydarth Road, Maesteg, South Wales, won damages at Cardiff County Court in February last year after a judge ruled in favour of him and his next-door neighbour, Robin Waistell.
The pair claimed the hazardous plant had encroached on to their properties from land owned by Network Rail and had reduced the value of their homes.
Both men were awarded £4,320 to cover the cost of treating the knotweed, while Mr Williams was entitled to a further £11,900 and Mr Waistell £10,300.
Three leading judges rejected an appeal by Network Rail against the county court decision in a ruling which paves the way for landowners to claim damages if the plant's underground roots or "rhizomes" have encroached on to their property.
However, the court reversed the finding that the pair were entitled to damages to cover the fall in the value of their properties because the knotweed was within seven metres of their homes - reducing each of their damages awards by about £10,000.
Speaking after the ruling, Mr Williams said his fight - which has been ongoing since he first complained to Network Rail in 2013 - will continue and he may have to return to court.
He said: "I haven't got the diminution of value, I have only got a couple of grand, which isn't worth all the hassle I've had.
"This isn't the end of it."
The bamboo-like plant, which grows quickly and strongly and spreads through its underground roots, can undermine the structural integrity of buildings and is expensive to treat.
The county court judge found that, although there was no actual physical damage to either man's property, the knotweed rhizomes had extended under each of their bungalows.
Stems of knotweed behind Mr Williams's home sometimes knocked against his windows and had "blighted" his property, the judge concluded.
He said Network Rail's efforts to treat the "pernicious weed" following the homeowners' complaints in 2013 were "not adequate or reasonable".
Japanese knotweed has been present on Network Rail's land at that location for at least 50 years.
Announcing the Court of Appeal's decision, Master of the Rolls Sir Terence Etherton said: "Japanese knotweed, and its roots and rhizomes, does not merely carry the risk of future physical damage to buildings, structures and installations on the land.
"Its presence imposes an immediate burden on landowners who face an increased difficulty in their ability to develop, and in the cost of developing, their land, should they wish to do so, because of the difficulties and expense of eradicating Japanese knotweed from affected land.
"In this way, Japanese knotweed can fairly be described as a natural hazard which affects landowners' ability fully to use and enjoy their property and, in doing so, interferes with the land's amenity value."
However, the judge - sitting with Lady Justice Sharp and Lord Justice Leggatt - said the homeowners would not be entitled to damages for the reduction in the value of their homes due to the presence of knotweed within seven metres of their properties.
The court refused to give Network Rail permission to challenge the ruling in the Supreme Court.
A Network Rail spokesman said: "As many gardeners know, Japanese knotweed is invasive and requires several years of treatment to remove.
"Once identified, Japanese knotweed growing on our land is entered into a treatment programme.
"We will continue with this established regime, which complies with legislation and helps us run a safe, reliable railway.
"Network Rail is aware of today's ruling by the Court of Appeal and is considering its implications."