Most of the Fleet is buried in a Victorian brick tunnel (courtesy of Bazalgette) - a beautiful thing in itself. The Sewermen who took me down there know all the byways and branches and there are places where things gather - near sluices, level changes, tight bends, junctions etc.. Whilst I was there I found a silver Irish 18th century ring and a sixpence by 'panning'.

There is a long out of print antiquarian (19thcentury?) book on the sacred springs of london which I have never seen - it's probably extremely expensive now. You can still visit the 'Clerks well' - which gave Clerkenwell its name - by appointment - in the basement of an office building off Farringdon Road. This was a sacred spring I think and was probably the reason that St John's priory and Charterhouse were founded nearby.

Thames Water's policies mean that they no longer recruit sewermen - the youngest I met was in his forties. They have/had a labyrinthine, down to earth knowledge of this immensely complex system - a knowledge which has generally been passed on orally - and which will soon be lost - just like the rivers themselves.