‘After we’re married,’ he said, ‘I can’t imagine wanting another woman.’ The doorbell rang a third time. It was the dancer. She had come for the weekend. ‘I’m not married yet,’ he said.

When I say ‘I will be true to you’ I must mean it in spite of the formalities, instead of the formalities. If I commit adultery in my heart then I have lost you a little. The bright vision of your face will blur. I may not notice this once or twice, I may pride myself on having enjoyed those fleshy excursions in the most cerebral way. Yet I will have blunted that sharp flint that sparks between us, our desire for one another above all else.

King Kong. The huge gorilla is at the top of the Empire State Building holding Fay Wray in the palm of his hand. A bevy of aircraft have been sent to wound the monster but he brushes them away as you would a fly. In the grip of desire a two-seater bi-plane with MARRIED on the side will hardly scratch the beast. You’ll still lie awake at night twisting your wedding ring round and round.

With Louise I want to do something different. I want the holiday and the homecoming together. She is the edge and the excitement for me but I have to believe it beyond six months. My circadian clock, which puts me to sleep at night and wakes me up in the morning in a regular twenty-four-hour fashion, has a larger arc that seems set at twenty-four weeks. I can override it, I’ve managed that, but I can’t stop it going off. With Bathsheba, my longest love at three years, the faithful ticker was cheated. She was so little there that while she occupied a fair stretch of time, she filled my days hardly at all. That may have been her secret. If she had lain with me and eaten with me and washed scrubbed and bathed with me, maybe I’d have been off in six months, or at least itching. I think she knew that.

So what affects the circadian clock? What interrupts it, slows it, speeds it? These questions occupy an obscure branch of science called chronobiology. Interest in the clock is growing because as we live more and more artificially, we’d like to con nature into altering her patterns for us. Night-workers and frequent fliers are absolutely the victims of their stubborn circadian clocks. Hormones are deep in the picture, so are social factors and environmental ones. Emerging from this melée, bit by bit, is light. The amount of light to which we are exposed crucially affects our clock. Light. Sun like a disc-saw through the body. Shall I submit myself sundial-wise beneath Louise’s direct gaze? It’s a risk; human beings go mad without a little shade, but how to break the habit of a lifetime else?

Louise took my face between her hands. I felt her long fingers tapering the sides of my head, her thumbs under my jawbone. She drew me to her, kissing me gently, her tongue inside my lower lip. I put my arms around her, not sure whether I was a lover or a child. I wanted her to hide me beneath her skirts against all menace. Sharp points of desire were still there but there was too a sleepy safe rest like being in a boat I had as a child. She rocked me against her, sea-calm, sea under a clear sky, a glass-bottomed boat and nothing to fear.