A guitar at twenty-one. Three label deals turned down by twenty-four.

Carl Martin got his first guitar for his twenty-first birthday. Before that, nothing — no lessons, no band at school, no family full of musicians. Just a curious kid and an instrument he didn't yet know how to hold.

Within a few weeks he'd written more songs than most people write in a decade. Within a few more, the people around him had stopped listening politely and started listening carefully. Then he opened his mouth to sing, and the room went quiet.

By twenty-two he was living in a flat in Notting Hill paid for by Trevor Horn and SARM Studios, recording albums and being introduced around London like the next big thing. He was coming up at the exact same time as Ed Sheeran, and the two names got used in the same sentences by people who knew what they were looking at.

A publishing deal was signed. Then three separate major labels came in with record deals. Managers of the calibre of Clive Black and Matt Ross were around the table. Everything he'd never asked for was suddenly on offer.

"I didn't want to spend my life around people who were quietly hoping I'd fail. That wasn't why I picked up a guitar."

He said no. Three times. And he walked.

What he built instead is quieter, and, if you ask him, better. He works with other artists on their songs. If he likes what he hears, he writes a chorus on it — no invoice, no upfront, no retainer. If the record sells, he keeps a share. He writes short pieces of music for film, TV and drama — thirty to sixty seconds of upbeat lift that carries a scene. He writes for ads when the brief is right.

He doesn't perform much. He doesn't need to. What he needs is a room with the person making the thing, a guitar, and an hour. That's usually enough.