Five million people travel on the Tube every day. For a little perspective, the population of London is 8.9 million. That means, over half of Londoners, plus quite a few tourists, rely on the Tube to be on time and running every day.
To accommodate this many passengers, there are often over 540 trains in operation during rush hour.
Walk into any Camden Market or Covent Garden souvenir shop and you're sure to find one or two references to the London Underground. Maybe you'll find the map printed on a poster or perhaps a shirt that reads, Mind the Gap. These mugs from the Royal Shakespeare Company use the Underground map to identify central archetypes in Shakespeare's plays.
In 1908, Underground Exec Frank Pick launched a poster campaign to encourage Londoners to explore their city via public transit. A lover of art, Pick commissioned young artists to create innovative and vibrant poster designs. This campaign ran until 1939 and you can still find posters in the Underground today.