The crime writer warned a sell-out crowd at the Edinburgh International Book Festival that “the clock is ticking big time” for the character, who has twice been brought out of retirement for recent books.
Rankin, who is about to release the 20th instalment in the series, suggested the only way he may be able to keep writing about Rebus in future would be to go back in time.
He revealed that he had already decided against writing a new Rebus novel in 2017 – even though it will be 30 years since the first book, Knots and Crosses, was published.
Rankin pointed out to his audience that the titles from the recent Rebus novels had all be inspired by songs by dead singer-songwriters, including Jackie Leven, John Martyn and Billy Mackenzie.
He said: “There is a real resonance with mortality. These are late Rebus novels. I’m very aware the clock is ticking big time, with him having retired twice. This time he’s gone – he can no longer be a cop.
“There’s only so much I can do with him. I can’t believe in him as a private eye. I could go back in time. I could do early books, but I’d have to do historical research, which is boring.
“I could stop the clock. I’ve already slowed it down quite considerably. Any keen-eyed reader would go back to the first Rebus novel, which was published in 1987, see that he was 40 and think he is 70. But, in fact, he’s only about 65. Even at that, he’s still got mortality.
“Rebus was never meant to be a serial character. But he got beneath my skin. He just drilled into my head and refused to leave.
“When I brought him back, having retired him for the best part of five years, I was kind of terrified he would refuse to be there any more. But he was really excited to be back and it was such a thrill. Obviously part of him had been sitting in my brain, just waiting.”
Rankin said Rebus’s techniques were now at least a decade out of date due to changes since the introduction of a single police force in Scotland, which have “horrified” crime writers.
He added: “There maybe used to be cops like Rebus in Edinburgh. But there haven’t been for over a decade. I go to a lot of police retirement dos and meet some of the old-timers who say: ‘Oh yeah, we had someone like him’. They tell me stories so outrageous you couldn’t put them in a book.
“You wouldn’t get away with it now. They’ve got to be cleaner than clean now.”