In 1984, towards the end of my time at university, I drafted a letter applying for a job as an advertising copywriter. I was a history student, so I showed it to a languid friend who was reading English. He read it while lying on a sofa one sunny morning. “Well,” he said, wafting it back to me, “there’s too many words in it.”

I picked it up off the floor and read the opening: “Dear sir or madam, I wonder whether, by any chance, I might prevail on you …”

“See what I mean?” said my friend, lighting himself a cigarette and tossing the packet over to me.

I did see what he meant and, glancing over the letter again – and seeing things like “I realise that my application is bound to be something of a long shot” – I experienced successive waves of emotion. First, shame at my crassness; second, gratefulness to my friend for having vouchsafed to me the magic word – the key, no doubt, to his own elegance in English. The word was “cut”.

I went back to my own room to set about it. Once decluttered, the letter immediately seemed like the work of a plausible individual. It wasn’t that I’d suddenly learned how to write; more that I’d learned how not to write. It was a revelation and the first time I realised that my dream of becoming an author might actually be realisable.

As an undergraduate, I had occasionally sent articles speculatively to newspapers. They were always rejected, but sometimes with an encouraging reply – “Do keep us in mind, though” – that would have me dancing around the room. I was also perpetually fiddling with a story about a young man who shuttled by train back and forth between London and Yorkshire, leading two entirely discrete lives. It was a sort of northern kitchen sink drama, 30 years too late and overburdened with logistics. I even bored myself as I began a paragraph, “He walked through Camden to King’s Cross station …”, but in light of my conversation with my languid friend, this became, “At King’s Cross …”. By a simple cut, I’d performed a kind of sorcery: I’d levitated my protagonist.

While doing clerical jobs in London after graduation, I scrawled stories during lunchtimes or on the tube. My route towards publication was a tortuous one, but the watchword “cut” glowed ever-brighter, and on Sunday evenings, I’d take my notebooks to a pub with a red pen in my pocket. I recall those evenings as rainy, and just as the rain seemed to be washing away the sordid misadventures of the previous week, so I was purging my erroneous prose. “Was it tiredness that was afflicting him?” would make way for, “He was, he supposed, tired”, and if the new version was slightly cryptic, so much the better.

Before submitting my pieces, I typed them on a gigantic Imperial typewriter, a machine intolerant of second thoughts. Yes, there was Tipp-ex, which I always applied at first too thinly, leaving the superfluous word showing incriminatingly through, then too thickly, so that it dribbled down, taking out some perfectly good word on the line below. A breakthrough came in about 1990, when I bought an Amstrad computer with word processing, so that I could play with words much as other people were starting to play video games; and just as Pac-Man ate little dots, so my cursor ate words. I should have eliminated even more than I did, as I realised in 1999 when looking at the proofs of my first novel. But there’d have been no novel at all without the intervention of my friend.

I’ve often wondered whether it was key that he’d been to a private school, which I hadn’t. A private education inculcates confidence, and you need confidence to edit yourself, in that you must believe something worthwhile will survive the process. My friend, who’s still languid and still a friend, wouldn’t mind my bringing that up, but what I really want to say to him is a word I’m not sure I said at the time: “Thanks.”

• Andrew Martin is a writer. His latest novel, The Night in Venice, is published by Weidenfeld and Nicolson