In the 1930s, the Thames and its tributaries were home to the 4ft-long creatures. Now there are thought to be no more than 13 otters in the South-east.
But after a massive clean-up of the Thames and its tributaries, a project to return the otter is being launched. Wildlife experts hope the mammals driven away by pollutants will resettle in Stratford, east London, when it is cleaned up for the Olympics.
First, they would take up residence in the lower Lea Valley, then establish themselves in the Thames, repopulating the riverbanks.
Armed with an acute sense of sight, smell and hearing, the fast-swimming otter, with a wide-ranging taste for fish, frogs and small birds, could soon be popping its snout above the waters as far as 20 miles upriver.
The plan, by the London Development Agency (LDA) and the London Wildlife Trust (LWT), is to clean up the industrial wasteland, rebuild the banks of the River Lea and ensure there are enough fish and eels for otters to sustain themselves. The otter is still found in the clean upper reaches of the Lea beyond Waltham Abbey in Hertfordshire and in Essex.
The lower Lea Valley, where otters once lived in abundance, will be at the centre of the Olympic park, but it has become a dump for wrecked cars, shopping trolleys and other detritus. The riverbanks are carpeted with crisp packets and plastic bags and the water is an unwholesome cocktail of pesticides and chemicals.
The Olympic authorities want to encourage the otters first to set up home near Stratford, before expanding their territory. There have been fleeting sightings of otters in outer London in recent years, in Redbridge in the east and Richmond in the west, but they are not in central London.
Otters were brought to the brink of extinction in the decades after the Second World War by the widespread use of organo-chlorine pesticides in agriculture, which contaminated the fish they eat. By 1978, they had become such a rare sight that they were made a protected species. But now they have made a comeback across many parts of Britain.
Gareth Blacker, of the LDA, said: "The Olympics are not just about sport. They are a unique opportunity to regenerate a historic part of London, from the Thames, up the River Lea through Stratford to Hackney. The return of the much-loved otter to London would be symbolic."
After the Games, a "wildlife corridor" of trees, reed-beds and vegetation will be created to provide a permanent home for the mammals.
Carlo Laurenzi, the LWT chief executive, welcomed the planned habitat improvements and said the otters' return would also help the nationally endangered water vole, immortalised as Ratty in Kenneth Grahame's Wind in the Willows. The voles' ranks are being ravaged by mink, the tiny creatures' main predator. Otters "bodyguard" voles and out-compete mink for territory.
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