When the Central London Railway between Shepherds Bush and the City opened on 30 July 1900 it set the pattern for the world's deep level underground railways.
Well lit, spacious, electrically driven trains ran through tunnels bored deep beneath the surface while mechanical lifts eased passengers' journeys between the streets and the platforms. Opting for bored tunnels made building the line far less disruptive than the work involved with shallow cut and cover lines which had been the norm up to that time. Stations were built at the brows of high points in the tunnels to assist braking and acceleration.
The CLR was not the first deep level line but it was the first to bring together the essential elements of deep level railways built below other world cities throughout the 20th century.
It was preceded by James Henry Greathead's shield driven City & South London Railway between Stockwell and King William Street opened in 1890.
James Henry Greathead's original railway pioneered the concept but the tunnels were so small that the 'padded cell' cars were exceptionally cramped. Later the City end section was recut on a new alignment and remaining running tunnels enlarged to create what became the City branch of the Northern Line.
By contrast the CLR was a revelation. With its flat fare of 2 pence, the line was a success from the start, carrying 45M passengers by 1902*. The success owed much to the choice of a prime route where there would be a large number of potential passengers. A century later the Central Line is still one of the busiest on the London Underground.
Construction was remarkably quick. Work began in April 1896 and trains were running only 50 months later - a creditable effort considering the minimal amount of mechanical tunnelling aids available at the time. A top team of engineers was engaged for the work: Sir John Fowler, Sir Benjamin Baker and Greathead, who died before the line was finished to be replaced by Basil Mott.
But the CLR was not perfect. It gained a reputation for being smelly. Ventilation had to be radically improved. There was also an embarrassing problem with the first locomotives. They did not fit into the tunnels and had to be modified.
* Rails through the Clay, a history of London's tube railways. Desmond F Croome and Alan A Jackson