In the early summer of 2005, crime writer Simon Kernick was reaching the final stages of his fifth novel, a hefty, heavily researched thriller that “touched on the area of terrorism”. Then, on the morning of July 7, four young men joined the throngs of London commuters on their way to work carrying rucksacks stuffed full with explosives.

With 56 people dead and 700 injured, Simon abandoned the book, reasoning that people wouldn’t have the stomach for “a fictionalised account of something that has actually happened when that thing is as big, dramatic and tragic as that”.

The plot of his book didn’t, in fact, closely mirror what happened on 7/7 but, thematically, was too close to the bone. “You don’t want to make money out of someone else’s tragedy,” he says. “Anyway, it was abad book. I was taken over by reality.”

In the end, shelving the book cleared the way for a bigger triumph. His “other fifth book”, into which he dived immediately, sparked his current popularity and reputation as a weaver of frenetically fast-paced, high-octane crime narratives.

The idea for Relentless came from a nightmare he had at a crime convention (where else to have a nightmare?). He dreamed about getting a call from a friend who was being murdered down the phone line. The nightmare became the opening chapter of his subsequent ferociously freewheeling thriller about “a man being flung into a situation over which he’s got absolutely no control”.

The universality of his theme – an ordinary person suddenly submerged in an appalling predicament – made Simon confident that this book would be a success, possibly even his ticket to the hallowed upper echelons of bestseller-dom. He was right. Richard and Judy, who listed Relentless as one of their 2007 summer reads, said it was “a non-stop chase from start to finish”. It vaulted to number three in the Sunday Times bestseller list, as bestselling paperback thriller of the year.

Two years later, he can bask not just in the royalties but also in his new status — his publisher, Bantam, can now dangle the epithet ‘bestselling’ (no longer ‘cult’) before ‘writer’ in the dust jackets of his subsequent books: Severed, then Deadline; now, his eighth novel, Target.

Born in Slough but raised in nearby Henley, he left education in the early 1990s in the midst of a recession. Jobs were scarce, so he worked in bars, as a labourer, then, finally, in computer sales, despite the fact that he “had no interest in computers or sales”. It was then, while living in North London, that Simon, who had already dabbled with sci-fi writing in his twenties, turned his hand to penning thrillers.

“Doing a job that you don’t really want to do is a fantastic motivator to work at getting to where you want to be,” he says. “I wrote a hell of a lot while in London, working as a software salesman. I got myself 300 rejection letters over those years, writing books that will never see the light of day. It was great practice. What I would say to any would-be writer: ‘It’s a long old process’.”

Generally, his books are set in London, including Target, about a man who goes on a date in with a woman who gets abducted (he then becomes the target of anonymous killers). Simon has contacts in the Metropolitan police force and SOCA, the anti-terrorist branch and special branch, and occasionally gets disturbed by feedback.

“They tend to like some of my more dodgy characters, which I find a bit distressing. One of my characters was a policeman who doubled as a hitman who tends to kill the bad guys. They say: ‘I feel like that doing that sometimes’.”

Even in these glum economic times, crime thrillers sell well, frequently topping the bestseller lists. He thinks there’s an element of schadenfraude: “I think there’s an element of: ‘however bad my life is, it’s not as bad as this guy here’. You can cuddle up at bedtime and think: ‘out there bad things happen, but I’m fine here’. It’s a form of insulation, I suppose.”

Henley and the surrounding countryside serve him well as a quiet pleasant place to write his books, although rarely as direct inspiration for his tales about gangsters, drug traffickers or ruthless kidnappers. The pretty village of Hambleden crept into Relentless and part of Target is set in Buckinghamshire, but the main benefit of living in Henley is, for Kernick, the rolling countryside that envelops the town. “A lot of the plotting for my books is done by walking around the Oxfordshire countryside,” he says, adding that he’ll usually treat himself to a pint at the Angel on the Bridge after such thought-filled wanderings.

“You do spend a lot of time on your own,” says the divorced father-of-two, when asked if life treats him well. “And the first draft can be really tedious. I’ve been out of full-time employment now for eight years. I’m pretty much unemployable. I have to make this work. You’re always wondering how long it will last and that does make you a bit paranoid. But I do the job I’ve always wanted to do, since I was a young child. I can’t complain.”

l Target is published by Bantam at £12.99.