The City & South London Railway tube railway opened in 1890 with electric locomotives hauling three carriages. Originally only provided with small windows, these were soon nicknamed "padded cells".  These were replaced with standard tube stock when the line was rebuilt in 1923.  The Central London Railway briefly used carriages when it opened in 1900, but these were reformed into multiple units in 1902–03.   New carriages, nicknamed "Dreadnoughts", were introduced on the Metropolitan main line in 1910.  Also two rakes had a Pullman coach that provided a buffet service for a supplementary fare.  They contained a toilet and were built with steam heating; electric heating being fitted in 1925.  All carriages on the London Underground were replaced by the A Stock multiple units in the early 1960s.