Circle line (London Underground) and the C Stock trains have recently been replaced by new seven-car S Stock trains, in a programme completed in 2015. In 1863 the Metropolitan Railway, the world's first underground railway, opened in London between Paddington and Farringdon, connecting the Great Western Railway's relatively remote terminus at Paddington with Euston and King's Cross stations and the City, London's financial heart. In the same year a select committee report recommended an 'inner circle' of railway lines connecting the London termini that had been built or under construction. In the next year the Metropolitan District Railway (commonly known as the District Railway)
Romford–Upminster line saw an end to years of speculation about its future. There is only one intermediate station, at Emerson Park. At the connection west of the station to the main line was severed in 1968. The branch has just one signal, on approach to Romford. There were plans to link the line from platform six at Upminster to the reception tracks of the London Underground depot there. This would have allowed the transfer of London Underground D78 Stock units onto the main line to be hauled away by diesel locomotive for refurbishment at the Ilford depot. These plans were scrapped when