‘So why not take the secret to her grave?’ Drummond asked.

‘Because she was desperately worried about her son. She knew he’d never give up his life of crime and she felt he needed protection. And who better to provide it than the biggest face in the London underworld?’

‘So Slack just took her word for it that Terry Malone was her son?’

‘Not quite,’ I said. ‘He obtained a sample of the lad’s DNA and got it checked out. And it confirmed what Chloe had said.’

‘How do you know this?’

‘It was one of the things that came up in a conversation between Fowler and Slack at Malone’s funeral.’

Fowler had explained to us that he approached Slack at the funeral to ask him if he’d revealed to Malone that he was his father.

‘Slack told him he’d broken the news just a couple of hours before Malone was shot,’ I said. ‘That was why they’d been drinking champagne at Slack’s club in the West End. He wanted Malone to look on it as a cause for celebration. He told the lad that when Amy gave birth to his grandchild he would make sure the family was well provided for. He also told Malone that he wanted him to be heir to his illicit empire.’

‘The timing is significant if you think about it,’ Tony Marsden said. ‘Malone was killed about the time Slack was diagnosed with terminal cancer. That’s probably why Slack decided to come clean when he did.’

It made sense and was enough to convince me that we were right to focus on Slack as our main suspect.

First he discovers he has a son and is about to become a grandfather. Then he finds out he’s not long for this world, which prompts him to tell Malone that he’s his dad. But on that very night Malone is gunned down by a police officer during a raid on his home.

All this was piled on top of a pathological hatred for the police that had been built up over many years.

The final straw.

Drummond and the rest of the team now believed, as I did, that the case against Slack was stacking up. That it was looking increasingly likely that he had decided to seek revenge against the police following Malone’s death and Amy’s miscarriage.

But Drummond was at pains to point out that we still had no hard evidence.

‘I’m reluctant to bring him in again just to tell him that we know that Malone was his son,’ he said. ‘There’s an argument that he should have told us when he was questioned about the disappearance of the officer who shot Malone. But it’s not nearly enough to bring charges against him.’

And that was the problem. Slack’s fat lawyer would walk rings around us if we sought to prosecute Slack with nothing but circumstantial evidence.