Rebus is to return.

Ian Rankin, the best selling Scottish novelist and creator of the Inspector Rebus novels, is at work on an another Rebus mystery, he has confirmed at the Edinburgh International Book Festival.

Rankin also said he was working on other projects, and that a Rebus stage play was also being developed but that the character he has been writing for 30 years is to return in a new novel.

The new book will follow Rather Be The Devil, the 21st Rebus novel, which was published last year.

"I have just signed a contract for two more books, and one has to to be Rebus, so the next book I have to write is Rebus," he said.

"The one after that can be anything I want, so when the festival finishes, I will get the thinking cap on - I have got nothing at the moment, I have not got a title, I have not got a plot.

"I will start writing as normal in January, and by June, hopefully, touch wood, I will have another Rebus novel which will come out next Autumn."

Of the play, he said: "I have got lots of plans, there is a mooted TV series again next year, there is a possible Rebus play, which someone else is writing, not me."

Rankin said that the toll of time was beginning to show on his famous character - in the latest book he has been diagnosed with COPD, or Chronic Obstructive Pulmonary Disease, and has a shadow on his lung.

The writer said in the real world, Rebus would be long retired and unlikely to be working on crime investigations, but the lure of 'cold cases' means he can keep the character going.

Rankin added: "In the real world Ms Marple would be solving crimes, and Sam Spade would be doing divorces, he wouldn't be investigating murders necessarily.

"A good writer can convince you this stuff could happen."

He added: "The last two or three books have really been about encroaching mortality and Rebus not being able to get into fights anymore, and not being able to shoulder a door of a cheap apartment block in Leith.

"He tries to kick in a door and he limps for the rest of the book - because he is not a superman. He is fallible and fragile and that's interesting to me, and people often say to me, what keeps the series fresh when you have been writing for 30 years?

"The fact is that with every book - when I sit down to think about it - he has changed, from the previous book, he has changed from the guy he was 20 years ago - things have happened to his body, things have happened psychologically, philosophically, and that is the same for the other characters, and that is what keeps the series fresh."