“Right, you can see the similarities of these marks. We got a DNA match on George Marlow’s sperm with the blood samples from when he went down for rape, but that’s no help with Della. It also doesn’t help that he admitted having sex with Karen, and gave a very plausible reason, which seems to check out, for the spot of Karen’s blood on his sleeve. We’re sure his car’s the key; find that and I reckon we’ve got ’im. So keep at it.”

He moved on to the photos of the bodies. “The clearest evidence linking the girls, apart from the marks on the arms, is the way their ’ands were tied. Not the rope itself, but the knots.”

“Ah, knot the rope, eh, Sarge?” Burkin put in, still lisping.

Otley gave him the finger and replied, “Yeah, very funny . . . The knots are the same, but any boy scout could tie ’em. Now it’s your turn, Inspector . . .”

Tennison entered the room, munching a packet of crisps. Burkin waited while she sat down, then picked up from Otley.

“The sack that covered Della Mornay’s body was the usual type of hessian, no markings, but there were traces of sump oil on it. There was also sump oil found on Karen’s skirt. It doesn’t mean a lot, Karen could have got it off her own car.” He nodded to Tennison. “All yours,” and sat down.

She crunched the last few crisps and screwed the bag up, tossing it at the wastepaper basket and missing. As she bent to retrieve it they all saw the edge of pink lace. Otley, who never missed a trick, pursed his lips and crossed his legs like an old queen.

“Karen didn’t put up much of a struggle,” Tennison began, spitting a piece of crisp onto her jacket and brushing it off. “Her nails were short, clean, no skin or blood beneath them, but her hands had been scrubbed with something similar to the kind of brush used on suede shoes. Gimme Della’s . . .”

Otley passed her a blow-up of Della’s hands and she put it up beside the others. “I asked for this because you can see scratch marks on the backs of the hands and fingers. Now, Della did fight, and her nails, unlike Karen’s, were long and false. She lost them from the thumb, index and little fingers of her right hand.”

Burkin asked, “Did Marlow have any scratches on him when he was stripped?”