The Underground Electric Railways Company of London Limited (UERL), known operationally as the Underground for much of its existence, was established in 1902. It was the holding company for the three deep-level "tube" underground railway lines opened in London during 1906 and 1907: the Baker Street and Waterloo Railway, the Charing Cross, Euston and Hampstead Railway and the Great Northern, Piccadilly and Brompton Railway. It was also the parent company from 1902 of the District Railway, which it electrified between 1903 and 1905. The UERL is a precursor of today's London Underground; its three tube lines form the central sections of today's Bakerloo, Northern and Piccadilly lines.

The Baker Street and Waterloo Railway (BS&WR), also known as the Bakerloo tube, was a railway company established in 1893 that built a deep-level underground "tube" railway in London. The company struggled to fund the work, and construction did not begin until 1898. In 1900, work was hit by the financial collapse of its parent company, the London & Globe Finance Corporation, through the fraud of Whitaker Wright, its main shareholder. In 1902, the BS&WR became a subsidiary of the Underground Electric Railways Company of London (UERL) controlled by American financier Charles Yerkes. The UERL quickly raised the funds, mainly from foreign investors.