Early underground train, c 1935.
© National Railway Museum / Science & Society Picture Library -- All rights reserved
The first line on the London Underground, the Metropolitan line, opened in 1863, between Paddington Station and the City of London. The network quickly expanded. By the mid-20th century the tube lines were electrified. The building of good rail links between London and surrounding towns meant that people could live further from their place of work because they could travel more easily.