"Mind the gap" doesn't mean the same as "Watch your step" - it's specifically intended to draw the attention of passengers to the fact that in some stations the distance between the platform and the train is a little bit longer than in others.

Why anybody would find something to object about in that is puzzling. Not a problem many American vistors would have, I'd imagine. After all, it might even save your life.
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But "rectum face" - there's a programme they've been showing on our TV called "Brat Camp", about efforts to housetrain teenagers with mouths (and attitudes) like that. I don't know if they have an upper age limit for candidates...