It is also the environmentalists' biggest victory in several years. Long gone are the heady days of 1989 and 1990 when all three main parties vied for the green vote. Politicians, especially those in government, have lost interest. So has much of the electorate, according to opinion polls, and the media.
But at a time when housing development - the other main rallying cry for environmentalists - has been depressed, plans to bulldoze woods, meadows, and marshes and homes to make way for dual carriageways have kept interest alive.
The road would have severely damaged Oxleas Wood and neighbouring Shepherdleas Wood in the borough of Greenwich, south-east London. These are fragments of the ancient woodland which covered most of the country after the last Ice Age.
Much loved and used by local people, they also form a 180-acre, government-designated Site of Special Scientific Interest (SSSI) because they contain rare plants, insects and fungi characteristic of ancient woodland.
As well as erasing 12 per cent of the SSSI, the new road would have left small, isolated pockets of woodland and damaged a wider area through noise and pollution.
The threat to the woods made ELRC a national issue, but much of the local opposition stemmed from the damage it would do to the urban environment in nearby Plumstead, destroying 260 homes and adding to already high pollution levels.
The damage to wildlife and landscape caused by the construction of the M3 Winchester bypass at Twyford Down, Hampshire, is greater than that which would have been done by the ELRC. But Oxleas Wood has become as great a cause because it is a surviving fragment of nature in the suburbs.
'It has come to represent all that people cherish about their local environment,' said William Sheate of the Council for the Protection of Rural England. 'We can only hope this decision represents a new dawn in the Department of Transport.'
The European Commission is still pursuing a long-running complaint by local protesters that the Government's decision to approve ELRC breached the EC's Environmental Assessments directive.
In November, the Court of Appeal is due to consider a legal action against the Government launched by nine protesters. The case hinges on the exchange land the Government was legally obliged to offer to the local community to replace the woodland - lost in the construction of the new road. It offered an area of farmland near by which would have been fenced off for 10 years until new trees became established.
More than 3,000 people and organisations signed a pledge promising to use non-violent civil disobedience to stop the bulldozers. Protesters were confident that a much bigger mass action campaign than the one against the M3 bypass could have been mustered.