City and South London Railway

The City and South London Railway (C&SLR) was the first deep-level underground "tube" railway in the world, and the first major railway to use electric traction. The railway was originally intended for cable-hauled trains, but owing to the bankruptcy of the cable contractor during construction, a system of electric traction – an experimental technology at the time – was chosen instead.

Today, its tunnels and stations form the Bank branch and Kennington to Morden section of the London Underground's Northern line.

from http://en.wikipedia.org/wiki/City_and_South_London_Railway