Comparing notes with Hill and Porter, they found their experiences were broadly similar. Although the mood was still overwhelmingly positive, the fact that the expected result was yet to emerge was starting to be of concern. Word of the inquiry was starting to get around, and there were fears that whoever was responsible for the murders might get wind of the investigation and go to ground. The pressure was on to get through the lists as quickly as possible.

As the middle of the week arrived, Collins and Woods found themselves on their way to Charing Cross Hospital to interview Billy Moorwood, a former pupil of the school who now worked as a porter.

The two detectives arrived at the ward where he had been assigned to work and made their way to the nurses’ station to find out where they could locate him. The heavy-set black woman in the dark blue, scarlet-trimmed uniform of a head nurse looked around and could not see him so offered to page him instead. A few seconds later a shambling figure emerged from the other end of the long corridor of the ward. Moorwood was young but powerfully built, with a square jaw and slightly crooked nose.

One of the ring’s earliest victims, he looked far younger than his twenty-five years. His auburn hair looked an unfortunate shade of red under the bright fluorescent lights. Even from a distance his green eyes shone out like emeralds. He wore a long-sleeved pale grey top with navy blue trousers and black trainers. A red ribbon around his neck held his identity card. He had both hands thrust deeply into his pockets and whistled jauntily as he made his way towards them. Collins and Woods turned to face him, and Moorwood suddenly hesitated.

The announcement over the public address system had made no mention of anyone wanting to speak to him; it had simply asked him to come to the main nurses’ station. But the closer he got the more obvious it became that the request had nothing to do with hospital business. Moorwood’s pace slowed down more and more, until he was almost standing still, staring intently at the two officers.

He was still more than sixty feet away when Collins took a step towards him. And then it happened. The look of concern on his face suddenly turned to full-blown panic. Moorwood spun on his heels and ran.

‘Shit!’ Collins looked helplessly at Woods before taking off after the fugitive. ‘Come on,’ she called back to Woods as he started to follow her.

Moorwood had a good head start and his footwear was far better suited to the slick, tiled floor than the low heels Collins had chosen to wear that day. He dodged his way past oncoming doctors and patients, and suddenly took a sharp left. By the time Woods and Collins had reached the turn, he was nowhere to be seen.

Like all hospitals, this was a rabbit warren of interconnecting corridors and wards and private rooms. Moorwood undoubtedly knew the place like the back of his hand. There was no way in the world the two of them were going to be able to catch him.

‘Fuck,’ spat Collins, instantly regretting making the outburst in a public place. She was breathing hard, not out of exhaustion but out of sheer frustration. She looked over at Woods, who was slamming his hand against the wall in disbelief. He caught her gaze and managed a tight grimace. ‘We could call security, get them to seal the exits,’ he said.

‘It would take too long to organize. There’s only one thing to do now. Call Anderson.’

Billy Moorwood lived in the centre of a run-down estate of low-rise housing on the edge of Stockwell. The road leading to the main square was littered with rusting bicycles, discarded mattresses, abandoned car parts and huge piles of rubbish.

It had taken Woods and Collins less than twenty minutes to make their way there through the lunchtime traffic in the back of a speeding patrol car, blues and twos going like the clappers. It had taken a few more minutes for a van-load of uniformed back-up to appear on the scene. Anderson was on his way over too, but Collins had no intention of waiting any longer.

If Moorwood was their man, he would likely be trying to destroy any evidence linking him to the crimes. Time was precious. Every second they wasted would be another hurdle they would have to get over to make the case stick.

Ideally Collins had wanted Hill and Porter to make any key arrest, but with Moorwood she seemed to have drawn the short straw. The whole case still bothered her to some degree, but she had also been pissed off that Moorwood had done a runner and managed to get away from her. She didn’t like to let anyone get the upper hand.

Curtains had begun to twitch the moment the first police car arrived, and as the band of officers made their way through the debris and up the short path leading to Moorwood’s front door a small crowd gathered to observe them.

‘So much for the element of surprise,’ said Collins as they reached the door.

None of the officers had thought to bring an enforcer – the hand-held piston used to smash through hinges – so instead two bigger uniformed men jointly kicked just below the position of the lock. On their second attempt there was a splintering of wood and the door flew open.

With the uniformed team leading the way, Collins stepped into the hallway. ‘Police. Come out and show yourself,’ she shouted. There was no reply. She turned left into a small lounge, which held only a few items of scruffy furniture. Woods moved past her. ‘Kitchen’s clear,’ he shouted back.

Collins moved back into the main hallway. The two officers who had led the raid reached the door at the end and discovered it was locked, or more likely blocked from the inside. Collins stepped forward and slapped the flat of her hand against the wood several times. She heard movement.

‘Billy Moorwood? My name is Detective Inspector Stacey Collins. I need you to come out of there right now. If you don’t we’re going to break the door down. You have only a few seconds.’

‘Fuck off.’

‘I’m warning you. Either open the door yourself or we’re coming in. There’s no reason to make this any more difficult than it already is.’

‘Just fuck off and leave me alone. Just leave me alone.’

Collins turned to Woods. They had worked together long enough for him to know what she was thinking without her having to utter a single word. He headed back out through the front door and, with two more uniformed officers as back-up, moved around to cover the rear entrance.

‘This is your last chance, Billy,’ said Collins. This time there was no reply and she nodded at the two burly men, who once more kicked the door open.

Billy Moorwood was standing flat against the back wall of the room. A small, single bed was pushed up against the corner to the right. On the left was a narrow metal desk with a cumbersome-looking computer sitting on top of it. A small door glazed with semi-frosted glass led out to the small garden area.

In between the door and the bed was Moorwood. His skin was pallid and shiny as if he had become sweaty from running all the way there. His hair had fallen out of place and was totally unkempt. His face was the very picture of panic. He was still wearing his hospital porter’s uniform but the sleeve on the right-hand side had been rolled up. Moorwood held a Stanley knife, the blade fully extended, against the side of his wrist.

‘I’ll fucking do it,’ he gasped. ‘I’ll fucking do it, I will. You come one step closer and I’ll fucking do it.’

Collins’s eyes were drawn to the blade as it glinted in the light. She held up a hand to prevent any more officers from coming into the room.

‘Billy, you’ve got to listen to me. Don’t do this. Put the knife down and let’s talk about this.’ She took a step towards him.

‘One more fucking step.’ His voice was louder, more panic-stricken. ‘I’ll kill myself. I’ll fucking end it all right here, right now.’