Seal-spotting along the Thames

Some things are much better now than they were in the good old days. Like sewage systems, for example. How the Thames was brought back to life after being declared biologically dead in the 1950s (and became a haven for seals, cormorants and even dolphins): http://www.bbc.com/earth/story/20151111-how-the-river-thames-was-brought-back-from-the-dead?ocid=fbbrt