Paul continues his journey, travelling to Wales and the south of England. Visiting the River Wye, he sees how explosions of algae, caused by fertiliser runoff from farming, are part of a cocktail overwhelming the habitat. He travels to Hampshire, where Paul hears about the damage being caused to our rare and precious chalk streams, before discovering how regular sewage discharges on the coast are causing problems for Whitstable's famous oyster industry. Ending his journey in London, Paul finds a beacon of hope: the £4.4 billion Thames Tideway super sewer.