The film ended, followed by close-up stills of Karen’s badly beaten body, then her various appalling injuries. The last frame was of the bruising on her arms.

“OK, take a good look at these marks. Now we have the other victim, Della Mornay, who was killed approximately six weeks before Karen . . .”

The shot of the decomposed body was sickening. The close-ups showed her upper arms and what appeared to be bite marks.

“The foxes had a go at her, and the dog belonging to the man who found her. But look at the arms again: the same marks, almost identical to those found on Karen.”

Another body was flashed up on the screen. “Jeannie Sharpe, killed in Oldham in nineteen eighty-four. Again, note the bruising and welts on the upper arms. Fourth victim . . .”

Amson pointed to DI Muddyman and whispered, “You ready?” Muddyman climbed to his feet.

“Another video now, this time of Angela Simpson, whose family sent it to us. She was knifed to death in a public park in nineteen eighty-five. She was a hairdresser, well-liked kid, about to get married. This is her engagement party.”

The sweet face of Angela Simpson smiled into camera, showing off her engagement ring, then self-consciously kissing the young man beside her. Her smiling fiancé gave a thumbs-up sign, and Angela turned to the camera, laughing, and put her hands over the lens. Then she loomed very close and kissed the camera.

“During the house-to-house enquiries, George Marlow was interviewed. He had been staying in a bed and breakfast only fifty yards from the gates of the park where she was found. There were no marks on her upper arms, but look at this . . .”

There was a shot of Angela, lying face down, legs apart. Her hands were tied behind her back.

“The rope, the way the hands were tied were just the same as in victims one and two.”

There was a slight commotion as a WPC entered and tried to find Tennison in the dark. She delivered a brief message and departed, clocked by the men. Frank Burkin stood up to take DI Muddyman’s place.

“The fifth girl”—Burkin waited for the shot to appear on screen—“was Sharon Reid. She was sixteen, still at school, and worked part-time in a local beauty salon . . .”

When he had finished they broke for lunch, and the discussion was continued less formally in the canteen. Reading the menu, DC Lillie was reminded about the old woman, the one found in the chicken run. She had had similar marks on her arms to the others. He asked Sergeant Amson, who was in the queue behind him.

“Marlow was in the vicinity, that’s good enough for me to try and pin it on him.” He looked around Lillie to see what the hold-up was. “Come on, Burkin!” he yelled.

Lillie persisted. “But they didn’t all have clamp marks . . . Oh, not ruddy Chicken Kiev again! The garlic’s a killer!”