The ground where the Olympics is being constructed was some of the worst in London. You want industrial development and stinking factories away from the human population, and yet you want a cheap labor source around you. The river had these large communities of Irish settlers who were working on the docks and so on; gradually it spread eastward, and all the smelliest, nastiest, dirtiest things were dumped there and allowed to be, because nobody else wanted to be there. It had access to water, which was rapidly poisoned. Well, you can’t just change that overnight.