LONDON — I moved to London in 1997. I was 31. So, measuring by my London years, I’m only 24. Over the course of my London life I’ve accumulated at least 12,000 commuting hours — 500 days — in the London Underground, locally known simply as “the Tube.” Spending all that time underground was my choice. I enjoyed people-watching, reading books, or counting how many stops a person takes to put on make-up or finish a sandwich.