I knocked into a guy today while I was rushing to the tube (as you do). He apologized to me. Not in the harsh, fake "I'm saying 'sorry', but really I'm saying 'f-you'" way that many Londoners do. His apology was genuine.
The problem is: I knocked into him, and didn't even bother to say sorry (real or fake). Instead, I simply ignored him and kept plowing on.
I have officially become a London Asshole.
I guess my only saving grace is that unlike most Londoners (especially commuters in & around the tube), I do feel bad about it. And... I guess in all fairness, this may not just be a London thing, but a big-city thing. Or not.