Sat down on a train and pulled out my guide to Tanzania, whereupon the woman sat opposite me said "going anywhere nice?" (you couldn't see the title as the book was face down). Cue a frantic 40 minute discussion on the joys of travel and how good it is. I suspect we'd have chatted all the way to London if it weren't for her having to find to assigned seat, not the one she happened to sit in for a bit.
Nicely done Universe, nicely done.
 don't worry, this wasn't in London and as such strangers talking to each other is not only ok, it is considered normal.