Pollution of rivers is nothing new. In the twelfth century the inhabitants of Tavistock threw their rubbish into the Tavy, which luckily for them ran swiftly and did not silt up. The more numerous inhabitants of London were just as careless and from an early date severely polluted the Fleet brook, which entered the Thames where Blackfriar's Bridge now stands. In 1307 the Fleet was no longer navigable.

By the filth of tanners and such others [it] was more decayed, also by the raising of wharves, but specially by a diversion of the water made by them of the new Temple for their mills standing without Barnard's Casde.