Circle line (London Underground) the stations are shared with one or more of the three other sub-surface lines, namely the District, Hammersmith & City and Metropolitan lines. On the Circle and Hammersmith & City lines combined, over 114 million passenger journeys were recorded in 2011/12. The first section became operational in 1863 when the Metropolitan Railway opened the world's first underground line between Paddington and with wooden carriages and steam locomotives. The same year a select committee report recommended an "inner circle" of lines connecting the London railway termini, and the Metropolitan District Railway (commonly known as the District Railway) was formed to build
London Underground S7 and S8 Stock be fully served by the S Stock, due to its existing D Stock being newer than other trains that the S Stock was ordered to replace, as well as its recent refurbishment. The first S7 Stock train entered passenger service on the line between Olympia and West Ham on 2 September 2013. On 6 February 2014, the S Stock started running between Wimbledon and Edgware Road. The S Stock started services to Ealing Broadway on 13 June 2014, and on 17 June saw the start of commercial service to Richmond. On 16 January 2015, the Stock began running to Upminster.