Chloe turned her head away when my arm moved, fixing her gaze on the chair seat. The strap landed with an astonishingly loud crack, wrapping itself round the lower slopes of Chloe’s buttocks.

The effect was dramatic. Chloe’s head shot up, and she sang out “heee-uuu”. On one hearing, that soprano cry became one of my sexual tastes. I wanted to hear it again.

I also liked the shockwave in Chloe’s flesh, as the heavy strap impacted, though because she was fit it lasted only a second. I watched the miracle of her skin changing colour, a brilliant pink stripe emerging, blooming like a stop-motion flower, about three inches across, with sharply defined edges.

It bobbed and weaved, that stripe, as Chloe’s hips bucked in the seconds after that impact, throwing off the pain like a horse trying to throw a rider.

I waited until she’d settled and arched her bottom up again. I aimed to leave the next stripe just above the first, neither overlapping nor leaving a gap. That was misplaced confidence; no-one should expect to land a strap accurately without practice. The strap landed high, leaving a sloping welt across the top of Chloe’s left buttock and wrapping painfully high across her right hip. Chloe’s cry was higher in pitch and volume. It was the wrong sort of pain.

But I swallowed the apology I wanted to speak, because it would break the mood and make things worse. I said, in the harshest, angriest voice I could manage, “Get that bottom up, girl. You’re getting strapped. And keep still!”

That was kinder.

For the third stroke, and all those subsequent, I aimed for the fleshiest part of her buttocks, reasoning that since my aim was lousy I’d achieve a reasonable spread of strokes just by accident, and that at least the strokes would land somewhere well padded.