I didn't need any convincing that East London’s rivers are the most polluted in Britain. I walked from Stratford Station this morning to the Lea. The first polluted stretch of water was the Waterworks River as it passed under the High Street. Brown and white bubbles frothed the surface. Once I had reported it to the Environment Agency (0800 80 70 60) I walked down the Lea, south of the A11 junction with…