[jonrimmer]

The Taipei metro began operating in 1996, whereas the London Underground began operating in 1863. You can't really compare the two. The newest parts of the Underground, such as the Jubilee Line Extension that opened in 1999 are very clean, modern and spacious, but it's impossible to retroactively improve the rest of the network to the same standards while it's being constantly used by millions of people every day.

[dzhiurgis]

I wouldn't dare to say they are very clean. They are bit more cleaner than the old ones. The point is - nobody bothers to clean them.