Oh, and Barking is a town just East of London.

When they built the first sewers in London they built them for the rich folks up The West End, but they didn't want to dump the sewage in the river there because it would stink up the whole of London (This was in the days before sewage treatment works). So they piped it across North London and through the working class East End and into Barking Creek, from there it flowed into The Thames. This turned Barking Creek into an open sewer and gave it its new name Shit Creek (sometimes Shits Creek).

Another song that is associated with the journey of this sewer is "British Workman's Grave"

I'll see if I can find some links for you.