‘DS Forbes speaking.’ For a split second his clipped tones make me question my decision to call him. It’s Monday morning and he sounds stressed but I can’t ignore what I saw at the train station. Not if it takes us a step closer to finding Billy.

‘It’s Claire Wilkinson. Billy’s mum.’ I don’t know why I added that last bit. He knows perfectly well who I am but a lifetime of introducing myself at the school gates, talking to the kids’ teachers or ringing the doctor’s surgery has drummed it into me. Claire Wilkinson, Mark’s wife. Claire Wilkinson, the boy’s mum. I can’t remember the last time I introduced myself as Claire.

‘What can I do for you, Mrs Wilkinson?’

I can hear noises in the background, keyboards clacking and snatches of conversation.

‘I was at the train station on Friday,’ I say. ‘Temple Meads. I was on platform thirteen and I was …’ I falter. How do I explain the surety I felt that the ugly building I must have passed a thousand times holds a vital clue to my son’s disappearance? ‘I was wondering if you’ve searched the disused sorting office. There’s a lot of graffiti on it and Billy did say in his diary that he wanted to tag the station or one of the trains. Maybe he went there instead. Maybe he’s still there.’

DS Forbes doesn’t respond immediately. Someone in the same room shouts, ‘Yes!’ and there’s a smattering of applause.

‘DS Forbes?’ I say. ‘Did you—’

‘Yes, still here.’

‘Do you think it could be a lead? Do you think he might be squatting there? Sleeping rough.’

He makes a low humming sound. ‘I doubt it. That place is completely open to the elements. It’s basically a couple of floors on stilts. You’d be better off sleeping in a doorway.’

‘But he could be there?’

‘Billy could be anywhere, Claire. That’s the trouble. There are a thousand places in Bristol where he could be sleeping rough. Unfortunately we don’t have the time or resources to search them all. I’m still hopeful that we’ll get a lead as a result of the appeal. It’s still early days.’

‘But you’ll look? You’ll get someone to check it out.’

Another pause.

‘I’ll see what we can do.’