However, this latest threat was different and far more unusual. It had been sent to a whole team of detectives and to my knowledge that had never happened before. It also referred to our families, and that made it all the more alarming. Was it really possible that Aidan and my own mother were in danger? Did I need to warn them? Or was it best not to scare them since we still couldn’t be sure this wasn’t just a prank?

Amongst the detectives, Dave Prentiss appeared to be the most affected by it, presumably because he had only just become a father.

When a group of us gathered in the canteen for a sandwich lunch, he told us he’d been searching Google for stories about serious attacks on the police and what he’d found out had clearly worried him.

‘I didn’t realise there had been so many, especially in the States,’ he said.

He mentioned the case of a former soldier who shot five cops dead in Dallas in 2016. The same year gunmen in Mexico’s western state of Michoacán shot down a police helicopter, killing the pilot and three officers. And as recently as February 2017, a plot was uncovered to assassinate eight officers with the Pecos Valley Drug Task Force in the US state of New Mexico.

‘This is scary stuff,’ Prentiss said. ‘It’s as though nutters everywhere have declared open season on us.’

It might have been an exaggeration, but Prentiss did have a point. There had never been a time when coppers had felt so vulnerable. That was why the debate as to whether all officers in the UK should carry weapons was heating up again.

I had always been opposed to it, along with the majority of my colleagues in the Met, but in view of this new threat I began to wonder if I’d feel safer with a gun strapped to my waistband.

The afternoon was spent getting our act together and deciding who would do what in the weeks ahead. But it was difficult to focus because of the threat.

My thoughts kept turning to Aidan and my mother and I succumbed to the urge to text them both to make sure they were all right. Aidan replied with, ‘Why wouldn’t I be?’ But I didn’t respond for fear of making him suspicious.

Get a grip, I told myself. Aidan and Mum are OK. They’re safe. So stop worrying about them and get on with the job.

We needed to familiarise ourselves with the various files on the system relating to Roy Slack’s firm.

While we’d been tied up with the Harry Fuller case most of the information had been updated. Surveillance reports and financial records had been added, along with more photos and notes on members of Slack’s inner circle.