Five minutes later, we were on our way, walking down Brick Lane towards Whitechapel. When we passed Fournier Street, a group of kids came hurtling round the corner towards us, shouting and running full pelt. None of them a day over ten.

‘Hurry up,’ one of them yelled over his shoulder to his mates. ‘They’ll catch us.’ He lengthened his stride and the gang powered down the street, seemingly not bothered that they were on a collision course with the two of us and several other pedestrians.

‘Woah. Look where you’re going, fellas,’ Dan told them, his hand raised to indicate they needed to slow down.

‘Sod off, Grandad,’ the boy snarled, wild-eyed. His accent was familiar. He spat on the pavement when he approached Dan, narrowly missing his shoes.

As he passed us, I caught the glint of metal as he slid a knife out from his jacket sleeve. ‘Dan, leave it,’ I hissed. ‘He’s got a blade.’

Several boys were behind him, slapping each other on the back, eyes popping and jaws twitching. At the rear, four younger boys were sprinting to keep up. One of them was Ali, the boy from the flash mob, but he seemed completely different. Hyper and out of control. A few metres past us, he stopped dead and his three pals crashed into him.

‘It’s finish,’ Ali shouted back to them. ‘They got us block off. Look.’ He pointed. ‘Is that psycho, Kyle. He’s going to kill us. Run.’

For a fleeting moment, his face softened when he saw me, and relief flooded over it, but before I could say any more, the leader of the group of boys took off down an alley, yelling at the others to follow him. Within seconds, they’d scaled a wall into someone’s back garden.

Dan punched the air in frustration.

‘I wonder who Kyle is?’ I asked.

Dan shrugged. ‘Ali said, “He’s going to kill us.” Whatever it’s about, I suspect it’s a bit more than a couple of kids wagging school.’ He took his phone out and started dialling.

Maya, 12.30 p.m.

Maya, 12.30 p.m.

‘We’ve found some ID in one of the bags we recovered at the Brick Lane crime scene.’ Dougie was on loudspeaker in the car. ‘Belongs to a student called Sophie Williams. She’s doing A-levels at New City College.’

‘Any more detail?’

‘She’s seventeen and lives in Bow. Place is registered to a Mrs Williams. It’s 162, Saxon Court. Massive block on Hamlets Way, the ones that are being developed. Huge contractor banner outside.’

‘Thanks.’

‘Luckily for us, the bag was water-resistant. Bit of damage at the seams and pockets, but the technicians have dried out her phone. They’ve begun accessing her comms data.’

‘Hallelujah.’ I grinned at Dan.

‘Have you seen Suzie’s article?’ Dougie asked.

‘Yeah. We’ve just interviewed the shopkeeper she got her gossip from.’