A toxic mix of oil, chemicals and bits of tyre from roads is polluting English waterways and no-one is regularly monitoring it, the BBC has found.

Heavy rain forces run-off into streams and rivers. Campaigners say it causes “absolutely horrific” damage in places, including just downstream of where The Great British Bake Off is filmed.

England’s major road network has more than 18,000 outflows or drains.

National Highways runs the network and says it’s working to improve them.

Responsibility for monitoring water pollution in England rests with the Environment Agency.