The first underground railways

In 1854 an Act of Parliament was passed approving the construction of an underground railway between Paddington Station and Farringdon Street via King's Cross which was to be called the Metropolitan Railway. The Great Western Railway (GWR) gave financial backing to the project when it was agreed that a junction would be built linking the underground railway with their mainline terminus at Paddington. GWR also agreed to design special trains for the new subterranean railway.

Construction was delayed for several years due to a shortage of funds. The fact that this project got under way at all was largely due to the lobbying of Charles Pearson, who was Solicitor to the City of London Corporation at the time. Pearson had supported the idea of an underground railway in London for several years. He advocated plans for the demolition of the unhygienic slums which would be replaced by new accommodation for their inhabitants in the suburbs, with the new railway providing transportation to their places of work in the city centre. Although he was never directly involved in the running of the Metropolitan Railway, he is widely credited as being one of the first true visionaries behind the concept of underground railways. And in 1859 it was Pearson who persuaded the City of London Corporation to help fund the scheme. Work finally began in February 1860, under the guidance of chief engineer John Fowler. Pearson died before the work was completed.

The Metropolitan Railway opened on 10 January 1863. Within a few months of opening it was carrying over 26,000 passengers a day. The Hammersmith and City Railway was opened on 13 June 1864 between Hammersmith and Paddington. Services were initially operated by GWR between Hammersmith and Farringdon Street. By April 1865 the Metropolitan had taken over the service. On 23 December 1865 the Metropolitan's eastern extension to Moorgate Street opened. Later in the decade other branches were opened to Swiss Cottage, South Kensington and Addison Road, Kensington (now known as Kensington Olympia). The railway had initially been dual gauge, allowing for the use of GWR's signature broad gauge rolling stock and the more widely used standard gauge stock. Disagreements with GWR had forced the Metropolitan to switch to standard gauge in 1863 after GWR withdrew all its stock from the railway. These differences were later patched up, however broad gauge was totally withdrawn from the railway in March 1869.

On 24 December 1868, the Metropolitan District Railway began operating services between South Kensington and Westminster using Metropolitan Railway trains and carriages. The company, which soon became known as "the District", was first incorporated in 1864 to complete an Inner Circle railway around London in conjunction with the Metropolitan. This was part of a plan to build both an Inner Circle line and Outer Circle line around London.

A fierce rivalry soon developed between the District and the Metropolitan. This severely delayed the completion of the Inner Circle project as the two companies competed to build far more financially lucrative railways in the suburbs of London. The London and North Western Railway (LNWR) began running their Outer Circle service from Broad Street via Willesden Junction, Addison Road and Earl's Court to Mansion House in 1872. The Inner Circle was not completed until 1884, with the Metropolitan and the District jointly running services. In the meantime, the District had finished its route between West Brompton and Blackfriars in 1870, with an interchange with the Metropolitan at South Kensington. In 1877, it began running its own services from Hammersmith to Richmond, on a line which had originally opened by the London & South Western Railway (LSWR) in 1869. The District then opened a new line from Turnham Green to Ealing in 1879 and extended its West Brompton branch to Fulham in 1880. Over the same decade the Metropolitan was extended to Harrow-on-the-Hill station in the north-west.

The early tunnels were dug mainly using cut-and-cover construction methods. This caused widespread disruption and required the demolition of several properties on the surface. The first trains were steam-hauled, which required effective ventilation to the surface. Ventilation shafts at various points on the route allowed the engines to expel steam and bring fresh air into the tunnels. One such vent is at Leinster Gardens, W2.[10] In order to preserve the visual characteristics in what is still a well-to-do street, a five-foot-thick (1.5 m) concrete façade was constructed to resemble a genuine house frontage.

On 7 December 1869 the London, Brighton and South Coast Railway (LB&SCR) started operating a service between Wapping and New Cross Gate on the East London Railway (ELR) using the Thames Tunnel designed by Marc Brunel, who designed the revolutionary tunnelling shield method which made its construction not only possible, but safer, and completed by his son Isambard Kingdom Brunel. This had opened in 1843 as a pedestrian tunnel, but in 1865 it was purchased by the ELR (a consortium of six railway companies: the Great Eastern Railway (GER); London, Brighton and South Coast Railway (LB&SCR); London, Chatham and Dover Railway (LCDR); South Eastern Railway (SER); Metropolitan Railway; and the Metropolitan District Railway) and converted into a railway tunnel. In 1884 the District and the Metropolitan began to operate services on the line.

By the end of the 1880s, underground railways reached Chesham on the Metropolitan, Hounslow, Wimbledon and Whitechapel on the District and New Cross on the East London Railway. By the end of the 19th century, the Metropolitan had extended its lines far outside of London to Aylesbury, Verney Junction and Brill, creating new suburbs along the route—later publicised by the company as Metro-land. Right up until the 1930s the company maintained ambitions to be considered as a main line rather than an urban railway.