Waterloo & City line

The Waterloo & City line, colloquially known as The Drain, is a shuttle line of the London Underground which runs between Waterloo and Bank stations with no intermediate stops. Its primary traffic consists of commuters from south-west London, Surrey and Hampshire arriving at Waterloo main line station and travelling forward to the City of London financial district. For this reason, the line has historically not operated on Sundays or public holidays, except in very limited circumstances. The line was closed during the COVID-19 pandemic; since reopening in October 2021 it is open only on weekdays. It is the only fully-subterranean tube line; the Victoria line runs completely underground in passenger service but has a ground-level depot.

Printed in turquoise on the Tube map, it is by far the shortest line on the Underground network, being 2.37 km (1.47 miles) long, with an end-to-end journey lasting just four minutes. In absolute terms, it is the least-used Tube line, carrying just over 17 million passengers annually. However, in terms of the average number of journeys per kilometre it is the third-most intensively used line behind the Jubilee and Victoria lines.