In 1863 the Metropolitan Railway opened in London between Paddington and Farringdon. It was the world's first underground railway. It connected 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 report recommended an 'inner circle' of railway lines between the London termini that had been built or were under construction. In the next year the Metropolitan District Railway (commonly known as the District Railway) was formed to build and operate a railway from South Kensington to Tower Hill. The Metropolitan western extension opened in 1868 from a new station at Paddington to South Kensington. By May 1870 the District railway had opened its line from West Brompton to Blackfriars via Gloucester Road and South Kensington, services being operated at first by the Metropolitan. In 1871 the District had built a terminus at Mansion House, and on 18 November 1876 the Met opened its terminus at Aldgate. Due to conflict between the two companies it took an Act of Parliament before further work was done on the inner circle. In 1882 the Metropolitan extended its line from Aldgate to a temporary station at Tower Hill and the District completed its line to Whitechapel. On 6 October 1884 the temporary station was replaced with a joint station and the inner circle was complete. The Metropolitan provided the clockwise or 'outer rail' trains, the District the 'inner rail' or anti-clockwise.