‘Good idea,’ he says. She turns the knife and slices through the white locks. Underneath there is a silver furze, nicked here and there by tiny scars. She had imagined that people have round heads, but of course they don’t. Sir John’s is long and fluted with angles, slightly asymmetric, with a ridge here and a point there. She clears away the sodden hair and wipes the bristle with some linen soaked in wine. Now that the hair has gone it is easy to see the indentation and there is even a greenish tinge to the skin. Again she presses her fingers to the skin and she can feel the grating of the bones.

‘There is nothing for it,’ Mayhew says.

She nods and cuts, holding her nerve even while blood pours from the wound.

‘Scalps always bleed mightily,’ Mayhew says.

The skin wrinkles around the cut, pulling back. There is a thin veil of pale pink flesh that she needs to slice through. Then there is the bone, the colour of old teeth.

‘Linen,’ she says, and she retracts the blade. Mayhew wipes the wound with wine and for a moment they see thin cracks in the depression, such as on an egg. He nods. With the tip of the knife she touches one of the pieces of bone. Sir John gurgles and moves his tongue.

‘Hold him,’ Mayhew calls and he grabs Sir John’s head to keep it still. Katherine touches the bone again, this time letting the tip of the knife slip to the edge of the fragment. She probes further. Her hands are steady though her heart is fluttering. Then she attempts to lift the fragment away, to prise it from the skull. It comes, but with it comes a splurge of blood, thick and dark, that wells from the wound and pours down into Sir John’s ears.

‘Good,’ Mayhew says. ‘That might be the sanguineous swelling.’

Sir John makes another noise, deep in his throat, more like a dog than a man, and she fears the worst, but Mayhew has placed the clay pot of wine on the old man’s chest, and concentric rings appear in its surface to let them know he lives and breathes. After that there seems nothing else to do but stitch Sir John’s scalp back together. She uses her own hair and makes the smallest stitches she can, taking her time while Mayhew sees to the rest of the wounded as they come limping in. When she has finished she wipes Sir John’s wound with more wine and egg whites and then his face with the last of the rose water.

His eyes flutter and he opens them and for a moment he is terrified.

‘All is well, Sir John,’ she says. ‘All is well, only don’t move.’