The first time we were called into Mr Edwards’s office Billy tried to explain that graffiti was his way of leaving a mark on the world. He might not be remembered for winning a trophy for sport or drama but everyone knew who DStroy was. DStroy didn’t care how tall a building was or how risky it was to tag it. DStroy thought his teachers and the police were sleepwalking sheep carrying out the orders of hypocritical politician scum. Who were they to say he couldn’t express himself the way he wanted? Tagging wasn’t vandalism – it was art.

Mark called him a fucking idiot. He said respect was earned by working hard, not by scribbling on school property, and he was ashamed to call Billy his son. I saw Billy flinch just for a second before he muttered, ‘You’re one to talk about respect,’ under his breath. Mark didn’t hear him and I wasn’t about to ask Billy to repeat himself.

I hoped it was a phase, the graffiti and the defiance. I fell out with my own mum when I was about the same age as Billy. I felt so grown up and independent and I struggled with the fact that my parents still had so much control over my life. If Mum insisted Dad pick me up from a party at 10 p.m. instead of letting me stay until 11 p.m., or confiscated a lipstick I’d bought because it was ‘tarty red’, I’d argue back as though my life depended on it. I knew what was best for me, not her. Didn’t she know how pathetic it made you look in front of your friends to be picked up before all the others? Didn’t she remember how important it was to have the same shade of lipstick as everyone else?

I wasn’t soft on Billy when he got in trouble with the school. I backed Mark one hundred per cent when he told him he was grounded for a month, but I felt it was important to talk to Billy too, to understand why he’d done what he’d done so we could prevent it from happening again. Mark accused me of mollycoddling Billy but I wouldn’t back down. Shouting and screaming at him would only widen the gulf between us and I didn’t want to be a stranger in my own son’s life. But he wouldn’t let me in.

I turn another page of Billy’s sketchbook and dab at the tear on my cheek but I’m too slow and it drops onto the paper. The ink escapes from the edge of the design and creeps, frond-like, through the fibres of the page. I never should have spent the night at Mum’s house. If I’d just been stronger. If I’d held my ground and told Mark to get out instead then Billy would never have disappeared.