Hawkins glanced at her mobile, noting that the voicemail she’d left for Mike half an hour ago still hadn’t merited a reply.

Obviously he was busy, but that hadn’t stopped him in the past.

She was contemplating whether to try him again when movement caught her eye. Chris Whelan was hurrying towards her office.

‘Ma’am,’ he panted, leaning in through the open door, ‘do you have a moment?’

She nodded, motioning towards the chairs in front of her desk.

Chris moved inside and wilted into one of the seats. ‘I thought you should see this straight away.’

Hawkins took the mobile phone he was holding out to her. A BlackBerry. ‘Is this what I think it is?’

‘Yes, ma’am.’ He swelled. ‘Colin Wilson’s phone. The techs just unlocked it.’

Hawkins glanced out into the still-empty operations room. ‘Where’s everyone else?’

‘Oh.’ Chris raised a self-conscious hand to the blotchy redness flowering on the pale skin of his neck. ‘Frank, I mean DI Todd, said I was working with DS Sharpe today, who … had to nip out. He told me to wait with the technicians until there was some news.’

She frowned, irritated by her team’s apparent readiness to cast the young recruit aside like superfluous baggage.

‘I … couldn’t find anyone else, so I brought the phone to you.’ Chris chewed the back of his thumb and stared at the desk.

‘Don’t worry.’ Hawkins pressed one of the BlackBerry’s buttons, lighting its screen. ‘You did the right thing.’ She scanned the icons littering the display, ignoring the one suggesting that Wilson had over two hundred unread emails.

She was about to open the message function when Chris spoke again.

‘I, er, took the liberty of checking texts and emails, ma’am. Nothing jumped out, but …’ his hands circled in mid-air, as if he were willing himself on, ‘… you might be interested in the map function.’

Hawkins nodded, grateful for the display of initiative, and selected the phone’s navigation software.

After a couple of wrong clicks, she found a list of recent searches, immediately feeling a jolt of excitement as she read the first result: 42 Priory Walk, Park Gardens Estate, Brixton.

She clicked on the entry, which opened to show a map of the walk from Tulse Hill station to the flat, pretty much confirming that Wilson had, as predicted, travelled by train to the place of his murder. But it also suggested that he had done so voluntarily, rather than being taken there against his will, although that didn’t guarantee his fellow victims had done the same thing.

Unfortunately, the route planner gave no clues to his prior whereabouts on the day in question, so she returned to the main list and started scrolling through the earlier entries.