‘Good,’ I said. ‘That should help us with identifying timescales and routes, and hopefully suspects. Someone may have seen the arsonist entering the shop.’ I paused. ‘We need to check dog walkers, postmen, joggers, road sweepers, people going to work, people coming home from night shifts and nights out. A lot of those people may not live locally so we’ll need to ring-fence mobiles and send ping-outs on social media.’ I tried not to look too obviously at Jackie who’d need to agree budgets. ‘What’s the latest with LfA?’

Alexej waved a print-out. ‘I’ve got the technicians’ report. The website lists the objective of the flash mob as taking back control of the streets. It says: “Young people can’t afford to rent a place in E1, and shopkeepers are losing their businesses because greedy landlords are hiking rents. Let’s take back control of the streets from the capitalists and opportunist entrepreneurs.”’

‘Perhaps the fire was about gentrification too?’ Dan eyed us all.

‘If I can chip in here . . . ?’ Jackie said, and I could tell from her tone that things were about to get a lot more complicated. ‘I’m not saying gentrification isn’t a genuine issue, but it’s possible that it was a front for both the flash mob and the arson.’ She spoke quietly but her voice conveyed authority. She joined Dan and I at the front of the room. ‘It’s the Trojan horse model of sneaking something under the radar. If you want to create a distraction, you pick a theme which is guaranteed to stir people up. That way, you maximise the chances of getting a big crowd.’

‘From what I see as a newcomer, it’s definitely the cost of living that bothers Londoners most,’ said Dan.

‘And the more faces and bodies you can gather,’ Jackie continued, ‘especially when they dress the same, the more difficult it is to see what’s going on.’

‘The masks?’ It was obvious now.

‘Precisely,’ she said, gauging the reaction to her words. ‘Masks aren’t just about group identity. They render people faceless. Group dynamics quickly shift from the inter-personal to a mob.’

‘Do we know whether LfA simply publicises these flash mobs or whether they’re the organisers?’ Shen asked.

‘We don’t know.’ I felt frustration bite. ‘Some of the kids mentioned a man called Frazer. Hopefully the technicians can find out what his role is.’ I took stock. ‘Moving on to evidence. Alexej, can you summarise?’

‘The exhibits are all catalogued. Loads of personal items.’ He clicked his screen into life and read off it. ‘Bags. Clothing. Phones. Keys. The speakers.’ He turned to face me. ‘Dougie’s sent through a list of the top priority ones. Any chance of the lab fast-tracking these?’