We were then told that the Commissioner had sanctioned the carrying of firearms by those officers who were authorised to use them.

That was all I needed to hear. As soon as the briefing was over I went to pick up a gun. At the same time I picked up a Taser for good measure and slipped it into my bag.

The pistol I signed out was a Glock 17, and I wore it now in a holster around my waist, cowboy style. It provided a degree of comfort even though I hoped I would never have to use it.

Despite everything that was happening, Drummond said he wanted us to continue doing our jobs. The emphasis had changed, of course. In the short term at least we were no longer focused on breaking up Roy Slack’s empire and finding evidence to bring charges relating to his involvement in organised crime.

Now we had to devote ourselves entirely to the task of finding out who was behind the murders and the threats. Other units within the Met were doing the same – the Murder Investigation Teams in Battersea and Clapham, the National Crime Agency, and the Cyber Crime division.

My remit continued to be to concentrate on Slack himself and to look for chinks in his armour. I started by getting an update from the team who were keeping him under surveillance.

I learned that he left his apartment at Canary Wharf at about six thirty the previous evening and went to his office in Rotherhithe where it appeared he had a meeting with some of the main faces in his organisation.

We hadn’t managed to plant any listening devices in the building so we did not know what was discussed. But we could guess.

When Slack left there he went straight back to his apartment and he was still there apparently.

I wondered if it was worth going to see him again, to question him about Marion Nash’s murder. Probably not, I decided. He would just tell me that he didn’t do it and had no idea who did.

I was aware that a couple of the team were coming round to the view that he might not be involved after all. I’d heard them talking. They weren’t convinced that someone with terminal cancer would unleash a pointless firestorm that would jeopardise their freedom during the final months of their life.

It was a reasonable explanation and one that I felt would gain traction if we weren’t able to link him soon to what was going on.