IAN Rankin admits he made a mistake with John Rebus. It was nothing to do with the character of his crumpled, curmudgeonly Edinburgh detective - it was his age.
He decided to write his novels in "real time" and made Rebus 40, which meant that 20 years later he'd have to retire. And much to the dismay of millions of readers, that's exactly what Rebus did five years ago in Exit Music. Rebus was out, Rankin had other things to do and he didn't miss him.
"It was a great opportunity to try different things. I wrote a graphic novel, a libretto for an opera. I wrote a film script based on a 19th-century Scottish novel that will never get made but was interesting to write, I tried my hand at song lyrics, and lots of short stories. I was really getting to stretch myself."
Then Rankin discovered the police had changed the retirement age, so he has duly revived the career of the detective whose passion for alcohol is matched only by his enthusiasm for vinyl music and his battered old Saab.
Rankin is in town to promote the 18th Rebus novel, Standing in Another Man's Grave, and as a guest at this weekend's Crime and Justice Festival, of which he has been a patron since its inception four years ago.
But he admits also to being worried about bringing Rebus back. "I wasn't worried about the reception, although I thought some people might say he's getting lazy and he's bringing him back because the other books haven't been as successful. What worried me was would Rebus' voice still be there?"
He needn't have worried. "He was champing at the bit to be let out of the little cell I'd put him in for five years."
In the new book Rebus is working as a civilian in a cold-case unit in Edinburgh and applying to rejoin the police. He is intrigued by a series of missing person cases that have some link to the A9, the major road that runs up the spine of Scotland. It becomes a sort of road movie of a novel as Rebus nurses his old banger up and down the country and realises "that there's much more to it than the crimes he's been investigating".
"The subtext would be to do with where Scotland is going," Rankin says. "Is it a unified culture, a unified way of looking at the world and hence should it be an independent country?"
Rankin has always wanted the Rebus books to create a picture of Scotland in the late-20th, early-21st century. So, the independence vote in 2014, what is his view? "Rebus would vote no, Siobhan [Clarke, his offsider] would vote yes. I'm somewhere in the middle. I need to be persuaded. Nationalism doesn't run through me like the word would run through a stick of rock."
He would like some answers to questions, such as how much of the UK national debt Scotland would be lumbered with? Would it get into the European Union? What about the oil revenue from the North Sea? "We need to see the facts and figures and we ain't getting them. At the moment it looks like Scots will say no."
When Rankin returns to Britain he has a promotional tour of Scotland (along the A9, of course), in England and later the US. And another book to complete by June. Another Rebus? "At this stage, I have no idea."
10am Peter FitzSimons on the Eureka Stockade
2pm Kerry Greenwood, Leigh Redhead, Angela Savage and Felicity Young on women and crime.
4pm Ian Rankin, Shane Maloney and Stuart Littlemore on heroes.
6pm Stuart Littlemore, Jeff Sparrow and Arnold Zable examine justice in Australian society.
10am Age journalist Sushi Das examines arranged marriages.
2pm David Day on Antarctica.
4pm Garry Disher, Leigh Redhead and Angela Savage on the state of crime writing.
6pm Ian Rankin in conversation.