I'd start, "dear Martin," but that isn't right. It's so friendly, so relaxed, and that's not us. We're taut ropes, you and I; not best friends. Even when we were friends, it was never for the best.

I'm writing to keep a promise. And that's where you'll laugh – because I don't keep promises. I made promises to you, to Adrian, to Pauline, and I broke every one. I have one promise, though, and that one I won't break. Even I couldn't betray a dead man.

Where does our story begin? It could begin in flowery southern England, or the heights of Scotland, or among the tall towers of Hong Kong. It could begin with a scruffy line of boys, shuffling through their first week of secondary school and forming friendships too quickly. It could begin with meeting up with the girls, and trying to be cool, and Pauline. But I think I'll start with a day that meant nothing, just so you remember.

It's not very specific; this happened a lot. Picture it. The five of us are in town, larking about, going from one place to another with no destination in mind. To the untrained eye we're a tight knit group, but look a little closer and you'll see the divides. First of all there's Adrian – he's likely to be slightly cut off, walking a step behind us and not catching every joke. The tallest of us all, he looks surprisingly little. Pauline and I walk either side of you and Douglas, but we're just bookends. You two are the main attraction. You're two pieces of the same stone, and you walk in our world like guests.

I know a little more about that, but I'll come to it later.

If you close your eyes, you can hear more layers. You won't hear Douglas – even if he does speak, it's quiet. Adrian can be loud, but now he holds back, chirping in at times but often ignored. When Pauline speaks her voice is cutting and cool, and her words planned out and concise. But it's you and I who come out top, your northern accent and my Scottish one overwhelming the others' southern whispers. We shout irrelevant things until people turn to glare at us, each trying to be heard over the other.

The picture is confusing, but I'm sure you know it well. So would anyone from our part of the world. We were just another clique of teenagers, so regular that we could have been part of the paved streets or grey-brown buildings.

I'll tell you now: I never felt a part of it. I played out my role wonderfully, but I was forever a semitone off your note. Martin, you'll never forgive me, but try to understand me. You don't know your own story. You never noticed what was playing out behind the scenes – if you had paid more attention, maybe it would have worked.