http://prosign.tumblr.com/post/33766157596/someone-has-made-fake-london-underground-signs-and

Probably another artist hoping to cash in!

Loved these. Well executed and accurately portraying the underground experience.

I don't think its someone rather its some people, independently.... I think some of these have been around for a few years

I think I saw one or two when I was in London a few years ago.