'I’ve got no road map. I trust it just to happen'. For the multi-million selling thriller writer Lee Child, the beginning of a new novel is a thrilling business in itself. With no plan whatsoever when he starts – by tradition, always on 1 September – he likens the process to a high wire act. 'It’s a risk because you’ve got no safety net. It’s like a movie stuntman who jumps off a high building, hoping the props people are going to get the air bag in position by the time he lands. For me, it’s essential not to have an outline beforehand, because I want to sit down to write with exactly the same level of interest as the reader who sits down to read. They’re excited to know what is going to happen next. And that’s exactly what I want to know too: what’s going to happen next? I revel in that ride'.

The genesis of Child’s 23rd and most recent novel, Past Tense, provides a fascinating example of how a story emerges in this freewheeling way. Once again, of course, it features taciturn knight errant Jack Reacher as he rights wrongs, dispenses moral justice, and saves innocent lives. As the novel opens, summer is coming to an end, birds are beginning to fly south for winter, and Reacher has decided on an epic migration of his own from Maine, to California. Once he’d established this beginning, Child asked himself, as he always does, how his first paragraph might dictate the rest of the novel.

'The mention of birds linked to a point I’d made about Reacher’s father in an earlier book. We don’t know much about him, but we do know that he was a marine infantry officer and a very tough soldier. So to humanise him I’d put in that his hobby was birdwatching. The fact that I’d then put all this bird imagery in the first paragraph of Past Tense gave me a hint that this should be a book about Reacher’s father. My own father had died just before I’d started writing the book, and so I’d been thinking about how well we can ever know another person, even a close relative. It occurred to me that there might be a secret to reveal about Reacher’s dad. But then a purely biographical book about his father would be sort of plain, so I needed another strand'.

'This second strand came from Reacher’s starting location. 'Stephen King lives in Maine, and so I thought of doing a Stephen King type set-up because he’s so great at them. He can have the most ordinary quotidian thing going on, but you absolutely know that something sinister is going to happen'. This led Child to invent Patty and Shorty, a young Canadian couple who are driving south to New York City with something to sell. 'I thought – okay, they’re young, they’re poor, their car is rubbish and it’s going to break down. And sure enough, it does break down near a lonely motel in the woods. It’s just a motel as far as we know, but the implicit bargain with the reader is - it’s going to be creepy!'. And creepy it most certainly is. Child’s two parallel strands build the suspense to an almost unbearable degree until they finally converge in the tautest of climaxes. No spoilers, but it’s fair to say that Reacher once again proves – as the strapline promises – 'a righteous avenger for our troubled times'.

The action takes place in and around the real New Hampshire town of Laconia, which is as far as Reacher gets on his migration south from Maine. It is also, as vigilant readers of Child’s previous novels will know, the birthplace of Reacher’s father. 'I originally picked Laconia simply because it sounds like laconic. Which could be the Reacher family motto as nobody says very much. I also mention in an earlier book that Reacher’s father’s perpetual refrain was: "I’m just a plain New Hampshire Yankee”. You know – thrifty and unemotional. So once I’d decided that Past Tense was going to be about Reacher’s dad it had to be set in Laconia'.

But besides ensuring such plot continuity, what is the secret to maintaining a compelling character like Reacher over 23 novels? 'The thing that really liberated me was choosing early on to make Reacher rootless. This gives me tremendous flexibility. Reacher isn’t tied to any location, and he also isn’t tied to any particular stratum of investigation, like say a police sergeant in one particular town would be. That way, the pitch of every story can be radically different'.

Whilst there’s no arguing with over 100 million sales of his novels worldwide (it has been estimated that every 13 seconds, someone, somewhere in the world buys a Lee Child book), I wonder whether he takes any notice of the critical reception his books receive. 'Do I read my reviews? Yes. Not because I need to find anything out though. I’ve lived with the book for a year and I already know where it’s weak and where it’s strong. And I’m never going to modify anything based on a reviewer not liking one of my novels'. Child does believe that respect for the craft of writing thrillers is on the up, however. 'In the past they would have been called pulp fiction or airport books, but I think people are beginning to realise that they can’t be dismissed as just fluff. Even though the subject matter is heavily plot-driven, they are beautifully assembled. And the writers working in this genre at the moment are some of the smartest and most brilliant people you’ll meet'.

Nor can Child’s novels be stereotyped as boys’ books. In fact, his readership consists of around 6o% women. He makes a convincing case for what he calls Jack Reacher’s particular and ‘multi-faceted’ appeal for women. 'Reacher likes women, and he respects them. The female characters in the books are not bimbos who need saving: most of them are tough as hell, as tough as Reacher a lot of the time. Even now in the 21st century, there’s still this issue about assertive women. They’re seen as shrill and somehow not as acceptable as assertive men. So I think women take vicarious pleasure in Reacher’s assertiveness'.

Child is also conscious of the competition his books face from other forms of entertainment including films and television: 'I have to be! I remember reading some research from the year I was born: half of all middle-class people in the 1950s said their prime leisure activity was reading. Now, of course, that figure seems ridiculous. We’ve got an infinite number of TV channels, an infinite amount of internet content that is designed to be endlessly absorbing. Everything is shorter, sharper and faster now'. How does this influence the way he actually writes? 'You just don’t hang around. You’re aware of having to move, move, move things along. I’m not complaining – it’s great, and it feels reckless because you’re just burning through the plot at a tremendous pace’.

It’s instructive to remember here that Child himself spent many years working in television before he turned to novel writing in the late 1990s. What if anything, did he bring from his time in TV to the craft of writing thrillers? ‘It’s actually much less than people think because they’re two very different ways of presenting stuff to an audience. There are lots of technical differences to do with point of view control, for example. But the major thing I learned in television was that it’s not about you, it’s about the audience. That teaches you to get over yourself real quick, and to think of the reader when you’re writing’. Television also taught him the skill of knowing exactly when to cut from one scene to another, including precisely where to end a chapter. ‘That never requires any thought from me because I dealt with 40,000 hours of television in my career and those rhythms imprint on your brain'.

Following two film adaptations starring Tom Cruise, the television is set to be the home of Reacher’s next screen appearances. Child has nothing but good to say of Cruise, despite the fact that his very un-Reacher-like proportions (he is 5’7” tall against Jack Reacher’s stated height of 6’ 5”) has come in for considerable criticism from fans. ‘Cruise is the nicest guy and I think one of the most talented actors of his generation. But the readers were not happy. Another thing I learned in television is: the public will think what they want to think. They are completely unmovable. So what I really want to do is involve the readers in choosing the new actor. They’re going to have ownership in the decision’. The platform on which the new TV series will appear has yet to be decided. ‘We had assumed Netflix because they had shown a lot of interest in the beginning but now there are other bidders joining the fight, which is great for us. So we’ll have to wait and see on that’.

Whilst we’re all set to meet a new incarnation of Jack Reacher on the small screen, it is the character’s very timelessness that perhaps best explains his huge and enduring appeal. Child sees Reacher as a modern character in a time-honoured tradition. 'The idea of the mysterious stranger is literally thousands of years old, and so many stories have depended on it. So the reader is connecting with a familiar paradigm even though they may not realise it'. The way in which the voice of a character also connects us to ancient versions of ourselves is also of great interest to Child. 'I think voice is incredibly important in writing. Because it’s only really in the last 150 years that we’ve been reading stories off the page. Prior to that, we had 100,000 years of listening to oral storytelling. So I think our brains are absolutely hard-wired for voice, and that’s why I wanted Reacher’s own voice to be distinctive from the beginning'.

What does the future hold for Jack Reacher, an intelligent, articulate man albeit one not much accustomed to talking? ‘Well on one level I have no idea because I don’t even know while I’m writing each book. But the fundamental psychological tension inside Reacher is that he loves being alone, but also worries about being lonely. That’s a very fine balance for him to manage. So I think that at some point his fear of loneliness will get the better of his love of solitude’.

Whatever Reacher’s future, it’s clear that we will discover it only gradually in hints and fragments, as perhaps befits Child’s marvellously suspenseful novels. 'I think finding out that way is very like real life. As I said earlier – how well do we ever know anybody? We certainly never hear anybody’s complete story', says Reacher’s creator, with complete conviction.