The first of five repeated programmes on a theme of nature
The River That Came Clean
Do you really love your local river? What do you expect to find there - leaping salmon ... or stinking mud?
Britain's inland rivers are the cleanest in the world; our estuaries are among the foulest.
But one great British estuary has come clean - the Thames.
A century ago Disraeli called the Thames ' a Stygian pool reeking with intolerable horrors'. Forty thousand Londoners died of cholera from drinking infected river water. Only 20 years ago the Thames, at low tide, smelled of bad eggs from Westminster to Woolwich. Ships gleaming white for the Festival of Britain turned black as hydrogen sulphide attacked their lead-painted hulls. The Thames salmon vanished for over a century.
Now the salmon is cautiously coming back. Its return has become a standard for measuring river pollution.
So how did the Thames become the cleanest metropolitan river in the world? Horizon looks at an environmental story that actually succeeded.
Editor SIMON CAMPBELL-JONES . Written and produced by CHRISTOPHER RILEY