I have a question that some of our UK friends might know the answer....
I was on the tube today. I went from Stop A to Stop B and exited. Exactly ten minutes later I re-entered Stop B and traveled to Stop C. I only got charged for one journey.
Is there an amount of time that one can exit a station and re-enter and not be charged for an additional fare? I only took one other trip so it has nothing to do with the daily cap.