The London train system is one of the worst in the world.

- It's very expensive.

- Different parts of the network are managed by different companies which creates a lot of confusion around tickets and smart cards.

- The stations are relatively ugly.

- Signs are confusing if you're not used to the system.

- Trains from different lines often share platforms. Sometimes two trains that have the same destination might stop at different stations and it's not obvious which train corresponds to which line.

- The underground trains themselves are often narrow; difficult to stand straight.

- They are often crowded so you often do end up having to stand up.

- Delays are common and trains don't come very often considering how many people live in London.