He still didn’t know when that would be. But he did know that he’d make sure he got his money’s worth out of Rosa Lopez. He would measure the success of the venture by how many people she killed and how their deaths impacted the Met and everyone who worked within it.

He wanted them to suffer both collectively and individually. He wanted to provoke panic and fear and confusion. He wanted to see desperation in the eyes of senior officers when they addressed the public and gave interviews. He wasn’t going to be satisfied unless the consequences were devastating. And he was sure they would be.

He was watching the news from the comfort of his padded leather armchair, switching between channels while drinking coffee and smoking a cigar.

The cops had let him walk because they’d known that they weren’t going to charge him with anything. How could they? There was no evidence. Nothing at all to connect him to the murder of DI Prentiss or the text messages.

He hadn’t planned on telling them about the cancer just yet, but he’d seen it as the only way of stopping the bitch from wasting his time. And it’d worked. He’d probably still be in the interview room if he hadn’t fessed up.

But he wasn’t sure how he felt about his condition no longer being a secret. Before today he’d only told two people – Terry Malone and Danny Carver. Telling Terry on the night he was shot dead had been hard. It was only weeks after he’d been given the news himself.

Pancreatic cancer.

As soon as the doctor told him he knew that he wouldn’t have long to live. Years before his own mother had been given the same diagnosis and so he’d learned all about it, including the fact that in some cases it can be hereditary.

She might have lived for up to six months if she hadn’t decided to spare herself and everyone around her a lot of agony and distress by taking her own life.

Slack had already made up his own mind to follow her example, and sooner rather than later. But instead of taking an overdose he would use the pistol he kept in the hidden safe along with his trusty knuckleduster and the laptop and phones that he didn’t want the police to get their hands on.

The safe also contained the suicide letter he had already written. It was in an envelope marked Metropolitan Police.

In the note he made it clear that he was responsible for the bloodbath. And he put the blame squarely on the shoulders of the Met for what they’d done to his father, his wife, his son and his grandchild.