the london county council had two tramway systems called the "north side" and "south side". for a long time, they had considered joining the two together. this would allow them to send trams from the "north side" to the central repair depot in charlton in south east london for overhauls. in 1898 it was decided to demolish the slum districts in the holborn area and rebuild them. this gave a chance to use the new streets for a tramway. in 1902, the council decided to build a tramway that was under the ground (subway). the subway went from theobalds road in the north to the embankment underneath waterloo bridge to the south. from there a line that was not underground would continue over waterloo bridge.