As we climb the hill on the far side of the harbour, smelling watered earth and eucalyptus, she is very serious. I remember once when we were writing a paper, Stella worked out a schedule of the time we could spend doing maths, eating, sleeping and making love. She was extremely stern about this last one, because she had identified it as a key area where we lost huge amounts of mathematical progress. Needless to say it was a failure: when I suggested, obedient to her instruction, that we get out of bed, she stretched out to the timetable she had stuck to the wall—the stretch, I remember, was one of the most beautiful things I had ever seen, her whole naked body reaching in a perfect curve from knee to fingertip, swaying as she neared the limit of her reach—and pulled it down, then tore it to pieces and threw them in the air. Before the paper snow finished falling she was already on top of me, and I don’t think we emerged again that day.