‘She cannot resist, can she?’ Dougie knew better than anyone how much grief Suzie had caused me over the years, and how she delighted in dredging up the most personal information in people’s lives.

‘Listen, was there literally nothing on the premises that could give us a clue to the woman’s ID?’

‘Nope. I’d have told you.’

‘No child’s hair grip or toy? I can’t get out of my head that she may have an elderly relative or kid at home.’

‘Sorry.’

‘OK. Speak later.’ I rung off and turned to Dan. ‘Let’s get over there, shall we?’

‘Do you think Sophie’s a significant witness?’ Dan asked.

‘Hmm. Don’t know. I’m curious about her relationship with these two lads. Particularly since one’s so young.’

Ten minutes later we arrived at Sophie Williams’ address. As Dougie had suggested, she lived in a vast block. The building stretched the length of the entire road and had five identical entrances at the front, on the street. A large scaffolding clung to the outside of the property with a green net suspended from the roof to the ground, to stop debris falling. We didn’t need to ring the buzzer as the door to the block was propped open and builders were traipsing in and out.

Sophie’s flat was on the third floor. The door was yanked open seconds after I rang the bell.

‘Where the hell have you—?’ A ghost of a face was staring at me, with a scruffy top-knot of strawberry-blonde hair.

A large black dog pushed its nose round the teenager’s legs.

‘Sophie Williams?’ I asked.

‘That’s me.’

‘DI Rahman and DS Maguire.’

Her face fell.

‘Were you expecting someone?’

‘Oh, my mum. It’s probably nothing . . . ’ Her words drifted off.

‘Could we come in? We’d like to ask you a few questions about yesterday’s flash mob.’

Sophie’s cheeks flushed with colour and she froze momentarily before pulling the dog away from the door and showing us into a sparsely furnished lounge. The spacious room had no carpet, just board with paint splatters and stains, and underlay remnants all over it. A threadbare two-seater sofa and matching armchair took pride of place in the centre of the room, both of which faced a boxy, old-fashioned TV set, which was propped up by a pile of text books.

Sophie was in the first year of her A-levels, she told us. Politics, history and law. ‘Mum and Dad got divorced last year and it’s been a nightmare. Mum’s had to go back to work and she’s really struggling.’ Sophie’s teenage features seemed younger than seventeen. ‘Dad’s got a new family and he’s taken my sister to live with him.’ Her sentence oozed with hurt. ‘There wasn’t room for me though.’ She gestured to the bare floor and the sagging sofa and the crappy telly.