Five-Minute Memoir: Julia Copus recalls how her father fixed her crumpled Yamaha trumpet

I'm standing at the full-length mirror in my mother and step-father's bedroom practising scales when it happens. The little cup-shaped mouthpiece gripped in my left hand is still warm from my breath.

Moments before, a gleaming Yamaha trumpet had been attached to it; at 13, it is the most valuable thing I have ever had charge of. As it happens, I know its value to the penny. The face in the mirror takes in my own look of wide-eyed horror. Fuck, it mouths at me – and it's only then, using all the courage I can muster, that I look down.

The trumpet is lying on its side on the floorboards, though clearly it didn't fall that way; clearly it's the bell that has taken the hideous, full-on force of the impact. Who would have guessed that brass can crumple like paper? Here is the proof of it, but still it seems extraordinary to me: a mass of tiny, sharp-edged wrinkles and creases.

I thank God that the house is empty at least: my mother and my hot-tempered stepfather have gone to Carrefour for the week's big shop. I bend and lift the trumpet by its leadpipe, with the useless carefulness of hindsight, and notice at the same time that I am shaking.

There is a lot of talk of money in this house – of bills and maintenance cheques. It is one of the many mind games that is played in the fallout of my parents' divorce. There are mumblings, resentments, accusations: some days, the whole house bristles with them. At 13, I don't understand the details: I cannot know what it is like to struggle with money. But that is not to say I'm not aware of the talk. It is like a thick miasma, a constant background radiation.

The trumpet was a 13th birthday present from my mother and stepfather, bought on the never-never. This confuses me. My feeling is that it was purchased grudgingly – and only after a long succession of arguments and tears – and yet it was they who purchased it, not my saintly father. A photo exists somewhere of the very day – almost the very moment – I received it. There I am at the dining table in my navy-blue school uniform, my hair cut short into a fashionable wedge. When I close my eyes now, I see the instrument as it was then: its shining valves, the coppery tint of its bell.

It doesn't take me long to weigh up my options; in reality, there is only one. The phone rings in my father's cottage on the edge of the New Forest. Forty miles away it rings, on the melamine counter next to the stack of neatly filed papers in his red-and-white kitchen. "Hello?" The nearness and familiarity of his voice almost throws me off balance again, but in a moment, between snatches of my own panicky exegesis, he is telling me, quite calmly, to put the trumpet back in its case, place the case in a black bin bag, wait until dark, and leave it in the front garden by the fence. "As near to the road as possible." His plan is to drive over later, when everyone is in bed. He won't even have to set foot on the gravel.

That night, I lie awake and think of the trumpet's strange, truncated body out there in the darkness. I picture the sodium glow from the street light catching on the bin liner in the rain; my father reaching over the waist-high fence…

A week or so later, I take out a little note I find curled in the trumpet's miraculously re-formed bell. It can't be much longer than a week, because I still haven't made my fortnightly visit to Dad's since the accident happened. 'Job done!' the note says, in his jaunty script. I lift the instrument from its case and turn it from side to side. The repair is astonishing. But when I look closely I see that there is a distinct marbling pattern covering the bell, like veins where the creases had been – faint but unmistakable signs of damage.

"You're pleased with it, then?" my father says on the phone that evening. I am standing upstairs on the landing, by the large front window, my forehead against the glass.

"Yes, Dad. Very. Thank you."

"Oh good, good. Because, to tell you the truth, I was a bit concerned about those ripples on the bell. But you didn't notice those? The only way to get rid of them is to have the whole thing re-lacquered. I'd need to take out a second mortgage!"

"No, Dad." I stretch my hand out against the cold glass of the window. I know that, because of the marks, I will have to tell my mother and stepfather what has happened. There is no way of avoiding this: it is something I will simply have to go through, and perhaps quite soon. But not now. Not yet. "No," I say. "I didn't notice."

Julia Copus is a poet. Her new collection, 'The World's Two Smallest Humans', is published by Faber, and has recently been shortlisted for the TS Eliot Prize