Let’s suppose the gardening is done, or, at the very least, the mower has refused to function; the hinges on the bathroom door, which have been sitting just that little bit askew since your brother-in-law walked into it in a panic after that Easter barbecue, have been set to rights; your spouse is visiting friends, the kids are set to camp out overnight in someone else’s garden and the dog, cat, rabbit, budgerigar have taken tranquillisers; there are no more Olympic reruns on TV.

You’re sitting alone, feet up, a glass of Wild TurkeyJamesonsCoca-Cola by your side. You should be perfectly relaxed - only, as Raymond Chandler almost wrote, there’s one of those mean, insidious winds blowing directly from the east, the kind that makes the nerve ends tingle and the body muscles twitch. Before you know it, all those feelings of frustrated anger or jealousy you’ve been harbouring towards your husband, wife, child, hamster for all these years break through the surface and won’t be denied. Fifteen minutes later, you’ve thought of the perfect crime. What do you do?

Do you rush to your notebook or open a new file on your computer and prepare to transmute this idea into the best-selling crime novel which will soon be stacked in huge piles air side at Heathrow and Gatwick, thereby guaranteeing fame and fortune and no further need to continue preparing next term’s lessons with 3C?

Or, do you wait until said husband, wife, etc, return and commit the crime?Which will bring the greatest or least frustration and sorrow? Which has the greater chance of success?

To put it another way, what on earth would possess you to devote almost all of that precious free time, when you could have been playing tennis, watching Notts County or replenishing the grouting, to writing a novel? A crime novel, at that. Is it the money or the fame? Or do you read crime fiction a lot and come across authors whose work gives you that sweat of excitement, that jolt of almost physical pleasure, the spur of ambition that says, “God! I would love to be able to write something half as good as that”?

It’s a truism by now (and it is true) that most writers neither sell large numbers of copies nor make very much money. If they are fortunate enough to have day jobs, they have not been so foolhardy as to give them up. And recognition? I’ve been personally responsible for some healthy deforestation to the tune of more than 90 published books, but I have only once (it was earlier this year, in the lift descending to the Northern Line platforms at Belsize Park) come face to face with anyone - other than close friend or loved one - reading one of my works in a public place. (And, yes, I did confess myself to her and share something of my excitement.) And while I have generally made a reasonable living, it is only in the past few years that I have been able to pay my various debts and bills comfortably from what my fiction has earned me.

There always have been - thank heaven and my agent - the TV things, the adaptations, radio plays, spots on Kaleidoscope, occasional book reviews and readings, day schools and my annual stint for the Arvon Foundation.

Writing one, or even a successful series of crime novels is not likely to make a fortune. If we’re lucky, very lucky and talented and tenacious and disciplined and hard-working and very, very, very lucky, it might just pay the rent.

I began my career as a writer while I was teaching full-time, working at a Stevenage comp and generally enjoying it.But I’d been doing it for 12 years and somehow I knew that if I didn’t stop, l’d be doing it, or something like it, for the rest of my life. And I wanted to try something else. it was one of those rare times when serendipity rules.

It was the mid-Seventies. The British publishing industry was experiencing a paperback boom. A writer friend had a friend who was a commissioning editorIand the result was that after reading Fifty Things You Should Know About Being a Hell’s Angel and taking two trips round the block on a borrowed Honda 50, Avenging Angel was published in 1975, all 125 pages of it, and Angel Alone commissioned. I handed in my notice, foolish lad.

What saved me was the western. New English Library had a series called Edge that was selling 100,000 copies a time, and every populist editor wanted a similar series on his list.

Fortunately, from the age of seven on (when he got me back from the Jesuits) my father had taken me to almost every western movie to play north London; those he missed, my nan made up for, and pretty soon I was seeking them out myself with purloined dinner money - Lash LaRue at the Caledonian Road Essoldo, Rod Cameron at that skinny little cinema south of the Archway that’s now an Irish dance hall, Wild Bill Eliot at the Court, Malden Road.

Someone was prepared to pay me for immersing myself in a fictional world and form I had thoroughly absorbed and loved; someone was going to pay me to practise how to write.

Lessons one and two: one, the most effective way of learning to write is by writing - and then rewriting - and then rewriting again - again; two, only write in a popular genre if you know it and respect what it can do.

Cynical attempts to write down, write pot boilers, write something trashy to make some quick money, generally end up producing the trash but not the money. After writing four, it now seems to me, lamentable, private eye novels in the Seventies, what brought me back to crime writing eight or so years ago, and triggered the first of the Resnick books, was the sheer pleasure experienced from reading Elmore Leonard. The humour derived from the juxtaposition of farcical and potentially violent situations and sharply observed characters, the vivacity of colloquial language, the way the story was spun along by conversation, the barely resolved sexual tension in all those “meet-cute” situations - the federal marshal and the psychic, the photographer and the Bio-Energetic cosmetic lady, the photographer and the nun.

Tone and structure, that’s what you can learn from other writers: beware of taking on too much style. The main reason my PI books didn’t work was that they suffered from an overdose of Raymond Chandlerisms and few of us can trade lines about the tarantula in the angel cake without them seeming stale. But do read other writers, lots of them, crime writing’s an increasingly broad church, the range of what’s permissible in form and subject matter seems to expand every day. Eventually, you’ll home in on those who raise those small hairs at the back of the neck, by the way they do the things they do.

So read Leonard’s La Brava, in my mind his best and most complex book. You thought nobody could find anything significant and different within the tired old British police procedural? Read Roses, Roses by Bill James. Is there a way, after Chandler, of reviving and adding depth and beauty to the private eye novel? Yes, and it’s James Crumley’s The Last Good Kiss. Want to write a funny, sexy gay love story and pretend it’s about crime? St Ella Duffy’s Calendar Girl. Want to write about issues without them deadening the characters or dominating the plot? The Hannah Wolfe books by Sarah Dunant.

The beauty of writing crime fiction is that it allows you to write about anything you want, anything that’s important to you, within an organisable form in which story-telling predominates but does not exclude other concerns.

Remember this: give the reader cause to read each chapter twice, once to see what’s happening on the surface, once, maybe more slowly, to see what’s happening underneath. Down in the sub text something stirred. If it didn’t, chances are it’s just a shallow book.

Don’t patronise your readers. Don’t trivialise. Don’t second guess what someone else might want. Ultimately the only rule for a crime writer is the same as for any writer, write the best book you can and do it so you can end up feeling proud that that’s exactly what you’ve done.

John Harvey’s latest Charlie Resnick novel, Easy Meat, is published by Minerva on August 27

Next week Helen Edmundson on writing a stage play