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In it, readers will find Rebus struggling with Twitter, young colleagues and all aspects of "the way 21st century policing has gone".

Speaking to an audience in Edinburgh, where the books are set, Rankin disclosed his style of character - a "working class, Scottish guy of a certain generation" - would no longer cut it in the modern police force.

"It's not so much they don't want them, it's that they wouldn't get them," he said of the force.

"I think the kind of people that join the police these days aren't the mavericks. They're not the Gene Hunts of this world - they're more like the John Simm character.

"What was interesting in Life of Mars was the dichotomy between 21st century policing - touchy feely and human resources – and that Gene Hunt character who's like a monster.

"Interestingly through the course of the series we all know he is much more complex than the John Simm character. And if you were in a bad situation, which one of them would you want standing up for you? You'd want the monster.

"For all his faults and all his difficulties, he's still the guy who will stick with you through thick and thin.

"Rebus is that kind of cop - he's the last of his kind. He's the last of this breed of dinosaurs from the 80s through the 21st century.

"And the series has charted that, charted the way 21st century policing has gone."

He added the same also applied to Cafferty, "the villain that runs Edinburgh, whose way of being a villain has changed".

"Cafferty in this book is surrounded by younger, hungrier, more venal villains who have no code of ethics whatsoever," said Rankin, 53. "They'll do anything.

"Whereas he's always gone, 'wait a minute, I don't hit women and I don't deal drugs', the young guys are going 'I'll hit women and I'll deal drugs. I'll deal drugs in school playgrounds'.

"You've got that notion that everything's changed, in many ways for the worse, and these two guys are left as the last of their kind, shrugging and going 'the world has no place for us anymore'."

Rankin, the UK's bestselling crime author, also announced gave a preview of his much-anticipated next novel, saying it would find Rebus even further out of his comfort zone while trying to navigate the police force's use of Twitter.

"He's of a generation where he doesn't understand it," said Rankin. "This idea that everything's contained in 140 characters is bizarre to him.

"I had a lot of fun with a young cop trying to teach him how to use it."

When asked about his relationship with local police, given his subject matter, he described it as "courteous".

"I don't want the books to become a PR exercise for the police," he said. "I only contact them if I have genuine questions."