The probe has travelled perhaps three inches and she guesses it is now in Sir John’s rectum. This is the thing she has been most anxious about, the actual slipping of the fingers into the anus. She dips her hand in the wine and then asks Richard to pour a few drops of oil of roses on her fingers. Then she guides them between the cleft of his spread buttocks and into the swirl of hair that marks his anus.

It is startlingly hot, almost burning hot. She nearly pulls them out. She presses on though. She slides her two fingers up to the second knuckle until she can feel the probe pressing through a hard puckering in the rectum wall. This must be the start of the fistula. Blood that is almost black oozes down between her fingers and snakes down her wrist. She puts her fingertips on the end of the probe and pushes from the other side, until something gives, and she can feel the probe’s nub against her fingertips. She breathes out.

Then she takes hold of the probe and levers it down, bending it, running it against her fingers so that it pushes its way out of Sir John’s anus with a gobbet of thickened blood and other corrupt matter.

Sir John mews in his sleep. Thomas twitches the sponge towards him. Katherine shakes her head. She sits back and looks at what she has done. She shudders, wishes she could give up, wishes herself elsewhere, but now she has started—

She twists a few strands of the horse’s hair into a loop and wraps it around the bead at the end of the probe that remains sticking out of the fistula. Then she pinches the anus end of the probe and gently tugs it all the way through, so that it takes with it the horse’s tail hair, just as if she were making a stitch in the cheek of his buttock.

She hears the men behind her leave the room one by one. The blood has drained from Richard’s face and Geoffrey is green.

‘No man should have to see his father like this,’ Richard says.

Katherine, on her knees behind Sir John, has a far worse view.

‘No man should have to see anyone like this,’ she says.

The smell of disease and corruption is powerful and Katherine cannot stop herself softly gagging. She uses a rag to wipe the blood from around the old man’s buttocks. His testicles are heavy, bald; the sack is like a pear, the skin whorled.

‘What next, Thomas?’

Despite having read Arderne’s work three or four times, she cannot remember everything.

‘Knot the two ends of the ligature, and then tighten them using the tendiculum, so that you obtain a straight line between the fistula’s opening and the anus.’ He coughs as he finishes.