Circle line (London Underground) and the C Stock trains have recently been replaced by new seven-car S Stock trains, in a programme completed in 2015.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)
London Underground Standard Stock and were later reclassified to become Classes 485 and 486. Apart from those cut up following accidents at Ryde depot, and other early withdrawals, most of these units were withdrawn between 1988 and 1991, when they were replaced by London Underground 1938 Stock. In October 1990, five cars were returned to London Transport, to form a Heritage Train. They worked under their own power between Fratton and Wimbledon, and were displayed at an open day at Morden Depot, celebrating 100 years of the Northern line. Standard Stock is used to describe six experimental cars built by five manufacturers in 1923,