‘In every case I’ve dealt with since joining the unit,’ said Blake, ‘victims have been delighted to be approached. They say that a conviction brings closure, often after many years of torment.’

‘But you do need consent to go ahead.’

He hesitated. ‘In almost one hundred per cent of cases.’

Fry nodded. DNA techniques had advanced significantly over the last twenty years in terms of sensitivity, reliability, and speed of results. They had become really important in revisiting old cases, reviewing the evidence recovered at the time. Preservation must have been good in Birmingham, because DNA deteriorated over time if it wasn’t kept cold and dry.

‘We had the element of luck,’ said Blake. ‘Our suspect had a DNA sample taken when he was arrested for robbery and possession of a firearm. Criminals don’t just commit sexual offences, but other offences too.

‘We firmly believe that murderers and rapists who think they’ve got away with it should no longer sleep easily, but should be looking over their shoulder.’

Out of the corner of her eye, Fry could see that Superintendent Branagh was nodding. It was a sentiment that no one with any sense could disagree with.

‘How was he arrested?’ asked Fry. It hardly mattered, but she felt a need to know every little detail, to make the picture come together in her mind. Perhaps it was just that the more detail she asked for, the longer it put off the moment when she would have to make a decision.

‘We had intelligence,’ said Blake.

‘Intelligence?’

‘Information from a member of the public.’

‘You mean one of the gang?’

‘No.’

Fry stared at him. She couldn’t imagine what other member of the public he could mean. There had been no witnesses to the assault, at least none that she could remember, and certainly none had come forward at the time. There had been plenty of appeals, of course. Lots of trawling from house to house in the area, hours spent stopping cars that used the nearby roads, and talking to motorists, lots of effort put into leaning on informants who might have heard a murmur on the streets. All to no avail. It was an offence with no witnesses other than the perpetrators and the victim.

Apart from her own statement, the only evidence she had of the attack were bruises and abrasions. And those faded with time, leaving only the crime-scene photographer’s prints to pass around a jury. As for the psychological scars . . . well, they didn’t show up too well in court.

‘Do I get to find out who the member of the public is?’

Blake pursed his lips. ‘Sorry. They’re on witness protection. You know how this works, Diane.’

‘Yes. They’re putting themselves at serious risk to testify. You must have done some pretty smooth talking, sir.’

‘You know, I don’t like to hear you call me “sir”, Diane. It was always “Gareth”, wasn’t it?’

‘It was, but . . .’