The dealer knew nothing about any Passat, black, blue or otherwise, so the team decided that the car seen near the school was probably the girlfriend’s. Or maybe Conrad had decided that his boy-racer days were over, and had traded in the Scorpio for something a little more sedate.

Once the information had been obtained, Porter’s team had shifted into top gear pretty bloody quickly. The first step was the establishment of an observation post. In the early hours – grateful for the cover of darkness as far as this part of the operation went – a dedicated Intel Unit had mounted one small camera on a lamp-post opposite an estate agent’s just off the Bow Road, and another at the back of the building to monitor what looked like a rear entrance/exit. These immediately began feeding live pictures back to Central 3000, as well as to a mobile tech team which was cutting up and broadcasting the images from inside a fully equipped van two streets away. A dozen or more officers from the Kidnap Unit were scattered around the area: in empty buildings and unmarked cars and on the street; waiting alongside a Special Events team, a hostage negotiator, paramedics and a group from SO19, the Firearms Unit.

All waiting for word of one sort or another.

By the time he managed to slip into a nearby sandwich bar for an early lunch, Thorne had been stuck for the best part of four hours in a car with the same SO7 officer who’d bored his arse off the evening before…

He carried the tray over to the table; pushed a mug of coffee and a plate across to the woman sitting opposite him.

‘What do I owe you?’ she asked.

Thorne took the top slice from a bacon and egg sandwich and reached for the ketchup. ‘Let’s hear what you’ve come up with first.’

He’d been surprised when Carol Chamberlain had rung up first thing, asking if they could meet. When she wasn’t at the Yard working an AMRU case, it was all but impossible to prise her away from her husband and her home in Worthing, which Thorne took great delight in calling Euthanasia-on-Sea. She’d explained that after she and Thorne had spoken the day before, she’d spent the whole afternoon making calls and then caught the evening train up. She’d told him that she’d had dinner with one old friend and stayed overnight with another.

‘Old friends?’ Thorne had asked on the phone.

‘A DCI I worked with on the Murder Squad for a few years, and a DS who retired same time as me. Both good blokes. Both useful.’

Thorne watched Chamberlain bite into a roll with rather more delicacy than he’d displayed himself. He was impressed by how quickly she’d got to work after they’d spoken. ‘You don’t waste any time,’ he said.

‘I didn’t think we had any time.’

Thorne brought her up to speed, told her about the surveillance operation on Conrad Allen’s flat. With the possibility of a child’s life at stake, he knew that she was right to think that time was not on their side, yet, that morning, every minute spent sitting and waiting for something to happen had seemed to warp and stretch until urgency had turned to inertia. The silence from radios had become deafening, and staring at the drawn curtains of the flat above that estate agent’s had been like looking through the wrong end of a telescope.

‘So, go on then,’ Thorne said.

Chamberlain wiped crumbs from her fingers. ‘I was right,’ she said. ‘Somebody should definitely have mentioned Grant Freestone.’

‘Because of the threat he made to Mullen?’

‘Because of that… and because he’s still wanted for murder.’

Thorne just looked, and waited for her to carry on. He could see that she was enjoying the moment of drama, that she relished the telling.

‘In 1995 Freestone got ten years for child-sex offences. He served just over half his time, was paroled in 2000 and became one of the first ex-cons to be dealt with by a MAPPA panel.’

Thorne nodded. Though he had never been directly involved, he was well aware of the Multi-Agency Public Protection Arrangements. The scheme had been established as ‘a statutory framework for inter-agency co-operation in assessing the most dangerous ex-offenders’. It was designed for those individuals who posed a serious threat to the public, ‘to manage and monitor their reintroduction into the community’.

To keep a watchful eye on the bogeyman.

‘Sounds like he was an ideal candidate,’ Thorne said.

‘He was, but I’m not so sure about the people who were supposed to be watching him. I don’t know exactly how it all happened, but it’s a wonder the scheme wasn’t shut down there and then.’

‘Teething troubles?’

‘Ever so slightly. Freestone was given a flat in Crystal Palace, which is why Bromley Borough Council helped put this MAPPA panel together. Then he got involved with a woman called Sarah Hanley a few months after his release; a single mother with two young kids.’

‘Ah. That would be a problem.’

‘It would have been if a slightly bigger problem hadn’t come along. In April 2001, Grant Freestone chucked her through a glass coffee table.’

‘Nice.’

‘She bled to death, and by the time anybody found her…’

‘Freestone was long gone.’

‘And still is,’ Chamberlain said. ‘Likely to stay that way, too, I would have thought. He’s certainly the nearest thing to a prime suspect anyone ever came up with, but it’s been so long I don’t think anyone’s looking for him very hard any more, or very often at any rate. He gets circulated once in a while, and the case notes are reviewed annually, but basically it’s even colder than most of the shit I get given to try and warm up.’

A waitress came alongside, gathered up the plates, asked if either of them wanted more tea or coffee. Thorne told Chamberlain he’d need to get back as quickly as he could, and handed over a five-pound note to cover the bill.

‘Was Tony Mullen involved with this second case at all?’ he asked. ‘With the Sarah Hanley murder?’

Chamberlain said that he wasn’t, that she’d spoken to the detective who’d headed that investigation and the subsequent hunt for Grant Freestone; the officer who, theoretically at least, still had the case. But Thorne was only half listening, having realised that he’d asked a redundant question. He knew that Tony Mullen could not have been involved, and he knew why.

‘I’ve written down all this bloke’s details,’ Chamberlain said. She slid an envelope across the table. ‘He seemed nice enough, though he was a damn sight more interested in finding out why I was asking than in telling me an awful lot.’

‘Par for the course,’ Thorne said.

‘I suppose.’

‘Aren’t you still a bit touchy about the ones that got away?’

Chamberlain took a compact from her handbag and flicked it open. ‘The older I get, the touchier I am about everything.’

‘Thanks for this.’

‘No problem, and I still owe you.’ Her eyes darted momentarily from her mirror. ‘I don’t mean for the tea and a ham roll, either.’

Thorne picked up the envelope and pushed back his chair. He knew she was talking about the incident a year before, when their questioning of a suspect had got horribly out of hand. He reckoned that each of them owed more than could ever be repaid. ‘I’ll let you know how everything turns out,’ he said.

Carol Chamberlain nodded and went back to reapplying her lipstick as Thorne turned from the table. As he left, she shouted after him. Apologised for forgetting the stuff for his back, told him that she’d stick some in the post.

He walked quickly back towards the car. He stopped off at a newsagent’s, bought two cans of Coke and a copy of Uncut without speaking a word. Thinking all the time, as he made his way back to the car, that Chamberlain had been right when she’d said that someone should have mentioned Grant Freestone. Someone… One of the several coppers he’d spoken to, probably. Jesmond, almost certainly. And why hadn’t Tony Mullen said anything?