The author said he had managed to finish writing a 44 Scotland Street story for the first time before its daily serialisation in The Scotsman gets underway.
Speaking at the Edinburgh International Book Festival, McCall Smith confirmed the return of his tales of life in Edinburgh’s New Town as he disclosed he has turned his hand to spy stories for the first time.
Among the characters he will be writing about is Donald Maclean, the British diplomat with Hebridean roots who became Society Russia's most effective agent and Stalin's star spy.
Part of the inspiration for 44 Scotland Street was Tales of the City, a series of novels by American author Armistead Maupin, which was serialised in the San Francisco Chronicle.
McCall Smith’s first story in the series, which is based on the residents of a fictional building in the real-life street, was launched in The Scotsman in January 2004.
The books, which follow the travails of Bertie, Irene, Domenica, Bruce, Angus and Big Lou, have developed a worldwide following, particularly in India, Australia and America, with fans flocking to the New Town to get a glimpse of the street where much of the action unfolds.
The new story, The Enigma of Garlic, which is expected to begin in The Scotsman by the end of this month, will see residents of Scotland Street gearing up for “the most anticipated event of the decade” – the wedding of Big Lou and Fat Bob.
McCall Smith said: “44 Scotland Street is one of my favourite series – I love writing it. I write a Scotland Street book a year.
“It is usually published as I write it, but on this occasion for the first time ever I have actually just finished it. I actually finished it yesterday.
“It’s set right on my doorstep and I’m very fond of all the characters. I love sitting down with them.
“It’s become a place of pilgrimage, although people do get very puzzled when they look for 44 Scotland Street because it doesn’t actually exist.
”Scotland Street has got a really lovely feel. It’s one of those really attractive streets where, because it’s so wide, you almost feel as if you’re in a courtyard. Other people are watching out for you.”
McCall, who read a new poem, The Principles of Espionage, said: “I do like a good spy story. In fact I’ve written a collection, The Private Life of Spies, which will come next year and is based on some real spies. I’m very excited about it.”
McCall Smith recalled his early success with his No. 1 Ladies' Detective Agency books.
He said: “It was initially published in Scotland with just 1,500 copies of the first edition. They decided they had to do a reprint. I was absolutely astonished. They said they were going to do another 500 copies. I told them ‘steady on, don’t get carried away’.
"I wrote four of those books before anything really happened with them. It was only when they were imported into bookstores into the United States that people suddenly began to write and talk about them. That’s when they took off.”