I was torn. Billy was fifteen years old. He was stretching his wings. He was a good boy. He was sensible at heart and I trusted him not to do anything stupid. And then he got into trouble at school for graffitiing the science block and Mark said that was that, he was grounded for two months and he was going to take away Billy’s bike. Only we couldn’t find it. And Billy refused to say where it was.

Now I jump as the gate clangs open and a man and woman in neon yellow vests with lanyards around their necks step through the gap.

‘Excuse me,’ I say as the man closes the padlock. ‘My name is Claire Wilkinson. My son is missing. He’s called Billy, he’s fifteen. I’m worried that he might be sleeping rough and—’

‘Not here he’s not,’ the woman says. She’s mid-forties with a half-inch of grey roots showing through her curly red hair. ‘Bristol Council.’ She gestures towards her lanyard. ‘We’re redeveloping the place. Waterside offices and homes. There’s twenty-four-hour security in place.’

‘You’re quite sure there’s no one sleeping rough inside?’

The man pulls on the padlock. ‘Not unless he’s a pigeon. And we’ll be getting them out ASAP too.’

I glance through the gates and try to imagine the building coming back to life – with glass in the windows and families sitting on sofas in front of their tellies and office workers wheeling back and forth in front of computer screens – but I can’t see it.

‘Thank you,’ I say. ‘I don’t suppose you know of any squats in Gloucester Road, do you?’

But they’ve already wandered off.

I am a couple of hundred feet away from the Arches and stuck in traffic when I see him, a heavyset man with a bushy beard. He’s riding a yellow-and-black BMX bike with distinctive blue-and-white tyres. He slips into the bus lane and undertakes me, his white trainers pumping the pedals as he speeds down Cheltenham Road. He looks almost comical with his large body balanced on top of the small bike and his thick knees spread wide. I remember how Jake laughed and said Billy looked like a circus monkey when he rode his Mafia BMX. It was a kid’s bike, he said. And he looked like an idiot.

Just like the man in the hoody.

It’s Billy’s bike. It has to be. I’ve never seen one like it, not with the same combination of colours.