Chase after happiness too hard, and it evaporates between your fingers. The trick is to let it creep up on you unawares. I am happiest when I am lost in my own imagination.

I people-watch and try to work out what their story is. And the best place to do this is the daily commute. Everybody uses public transport: rich, poor, old and young.

I try to pick up clues from the shoes they wear, the state of their fingernails, the depth of their laughter lines.

I have learned not to stare, and since the advent of smartphones, this has become a lot easier. Commuters tend to be so distracted by their electronic devices, they don’t often look up.

Also, people tend to kill their time by reading through old emails (always interesting) or by tapping out messages to friends (absolutely fascinating).

I like to call it feeding my novelist’s imagination. But you could just call it nosy.