How a Tesco chicken deal may have helped pollute one of the UK’s favourite rivers

The River Wye flows through Herefordshire where bird numbers - and their waste - surged in the year after the supermarket signed a deal with a local processor, Guardian investigation shows

A major deal to supply chicken to Tesco from nearly a decade ago may be linked to the ecological demise of one of the UK's favourite rivers, according to a Guardian investigation.

As the River Wye flows through mid-Wales to the Severn estuary, it passes through the so-called chicken capital of the UK, where an estimated 20 million birds are farmed in the river's catchment.