Dan left the nick in record time. It was a rush to get to St Katherine’s Dock for the flash mob, but he made it with a few minutes to spare. From his vantage point on a bench outside the Dickens Inn, he surveyed the area once more and checked his watch.

The back-up officers were on stand-by out of sight and the local Fire Station was on red alert. The WhatsApp message, which had been sent to the police dummy phone, had said to meet at 2 p.m. outside the Dickens Inn.

‘Can you hear me? Over.’ He spoke softly into the lapel mic.

‘All good,’ Jackie’s voice came back. ‘Alexej’s got the mobile. No texts or emails and nothing new on the forum.’

‘Thanks. Nil going on here.’

‘Standing by.’

Dan sat still. Vigilant. Eyes peeled. They were all praying there wasn’t going to be another arson attack.

Suddenly, three teenage lads appeared from nowhere, all attitude and swagger, swearing and joking, and carrying a set of mini-speakers which they set down in the square between the pub and the marina.

‘This looks like them,’ Dan said into his mic.

‘Received.’

Five younger kids arrived from the opposite direction, and an older teen lurked behind them, rugby-scrum muscles and a thick neck. The bruiser-guy gave a nod, and one of the youths who’d carried the speakers took out his phone. An up-tempo dance track burst into the April air. Almost in unison, the youths pulled black bandanas over their jaws and mouths, and Dan shot onto red alert.

‘Stand-by, stand-by,’ he said into his mic. ‘Black masks with the LfA logo.’

The kids leaped into action, whooping and shrieking excitedly. They sang along with the lyrics, throwing energetic moves in time with the beat. The air was a writhing mass of arms, wild and gesticulating, and waving at passers-by.

The track changed, and next it was rap. Two girls skipped over, giggling. Pulled up black bandanas and joined in.

‘That’s Sophie bloody Williams,’ Dan hissed into his mic.

She linked arms with one of the lads and shrieked with excitement as he spun her round. For her, it was exactly as she’d said – escapism.

‘My kids are crazy about hip-hop,’ said the plain-clothed PC who was standing a few feet from Dan.

Dan was silent. Last thing he needed was a talker.

One of the younger kids began handing out sparklers and matches, and encouraging people to light them.

Dan’s stomach lurched. ‘Sparkler alert,’ he said to control.

The music switched to a house track. The dancing continued, and so did the screams and laughter. Then, the music stopped, as suddenly as it had started, and the dancers all clustered in a scrum, congratulating each other and punching the air. Dan scoured the scene for the bruiser-bloke, but he was nowhere to be seen.