He stood there, grinning from ear to ear, pointing out particular rocks in the wall. He'd had a hand in repairing this ancient old thing some time last summer. And though I could tell he was awful proud of his achievement, I could only give a half smile, as I cast my mind back over the chain of events that had led us here, to a crumbling wall about to topple.

He'd had a tough time settling back in, our Billy. After we'd lived abroad, see. You think it's going to be easy coming back to the city where you were born and raised, to the culture and the social life that you've missed. But it's actually very difficult. Everything's changed while you've been away globe-trotting. The TV shows are different. Your friends have grown up or have moved to another village. There's new buildings where there used to be a car park, while old favourite haunts have been bulldozed. Reverse culture-shock, it's called. And it's worse for teenagers. Even things that should be positive, like being able to do his French GCSE in one year (and credit where it's due, get an A*), was just one more thing that marked him out as odd. And although he was at a good school, (which was costing me a bloody fortune!), he soon began cutting classes. That was bad enough, but then he started shop-lifting while he was playing hookey. And of course, he got caught nicking stuff. In Woolies. The big eejit.

I remember the phone call. His Dad was weeping. Ach, sure he always did over-react, I muttered. And then the chat with the kindly social worker in his woolly pullover. And then the stern talking to from the polis, obviously fed up delivering the same old message. I think I cried a lot that day, snuffling into a scrunched up tissue. How could he be so stupid, and throw away all these great opportunities? I'd got him into a grammar. I just bought him a new amp for his bass. I was all relaxed and friendly about his Goth friends coming round to watch Kerrang. I even let him have the occasional beer. Couldn't he see that I was the World's Greatest Mammy?

Oh well. Upon us all a little rain must fall. Led Zeppelin. I introduced him to them an' all. Maybe he'll remember that when he's bigger.

So this was his pay-back to society, his punishment for being greedy. He'd helped to repair this wall. And as the sun shone down on the stones, and on his beaming smile, I felt a tear trickle down my cheek.