Which railway became London’s first deep-level electric tube railway in 1890?

The City and South London Railway became London’s first deep-level electric tube railway when it opened in 1890. Its initial route ran between King William Street in the City and Stockwell in south London.

The railway used twin circular tunnels constructed deep beneath the streets. Trains were electrically powered, making the line different from the steam-hauled Metropolitan and District railways that had opened earlier in shallow cuttings and covered trenches.

The original King William Street section was later replaced because its terminal and alignment were unsuitable for expansion. The railway eventually formed the southern part of today’s Northern line. Several original stations, including Stockwell, were rebuilt or substantially altered as the network expanded.