LIKE ISABEL DALHOUSIE, the inquisitive heroine of his Sunday Philosophy Club series, British author Alexander McCall Smith is concerned with morality and philosophy. He says her thoughts are often his voice. 'Isabel is the closest to me of all my characters,' McCall Smith says, 'She often wonders about the implications of her acts and the issue of right and wrong. I'm very interested in moral philosophy, too. I guess in that respect she thinks some of the things I think.' Isabel is the fortysomething part-time editor of the Review of Applied Ethics - a philosophy magazine that addresses such questions as the limits of moralism. She likes to get involved in other people's problems, which she analyses at great length. In Friends, Lovers, Chocolate (Little Brown), the second of a planned series of four, Isabel takes on the case of a man who has recently had a heart transplant and is now plagued by terrifying memories he can't explain. Throughout, she ponders her feelings for the handsome Jamie, the young former boyfriend of her niece Cat. McCall Smith says that when he wrote the book he was more concerned with Isabel's physical and moral world than the mystery plot, which is 'almost in the background. You obviously want to have some plot. There must be some sense of forward movement to the narrative, but it doesn't have to be complicated or absolutely central'. He sips a cup of tea in the lounge of the Raffles Hotel during a brief stopover in Singapore on his way to Jaipur in India. There, he plans to finish writing Blue Shoes and Happiness, the seventh instalment of his international best-selling series, the No 1 Ladies' Detective Agency, which charts the adventures of Precious Ramotswe, a female private eye in Botswana. McCall Smith, who has won critical acclaim for the gentleness of his novels and their strong sense of place, says it's more difficult to make a good character more interesting than a murderer. 'What you can do is describe the struggle they have to be good,' he says. 'Mma Ramotswe has a bit of a battle sometimes with her thoughts, and Isabel has a major battle. To some extent, her temptation is Jamie. Most of us have a struggle to live a good life. It's very easy to lead one's life according to one's whim. It's very easy to be selfish and most of us are faced with the temptation to be so.' McCall Smith says that Isabel's approach to money (she's inherited enough not to worry about it) and how to use it (giving in anonymous ways to charities) is closely linked with questions he's asked himself since his new-found fame. Despite having written more than 50 books in 20 years, the 57-year-old was still relatively unknown until publisher Random House took notice in 2002 after an article on his series in The New York Times. 'Tremendous amount of luck,' McCall Smith says. The article turned his life upside down. The first novel in the series had an initial run of just 1,500 copies with Edinburgh publisher Polygon. The series has now sold more than 10 million books in English and been translated into 36 languages. It will soon be made into a television series by Mirage, the production company owned by Anthony Minghella and Sydney Pollack. Until three years ago, McCall Smith, who was born in what's now Zimbabwe, was a full-time professor of medical ethics at the University of Edinburgh, as well as an adviser to Unesco and the British government on bioethics. Writing children's books and short stories was a hobby, albeit a successful one. Now on an unpaid sabbatical, McCall Smith says he won't go back to his academic career and isn't planning to draw inspiration from his experience in law and medicine. 'I'm more interested in writing about characters,' he says. 'There are people who write a very good plot, and people who write about their professions. But I'm not one of those.' McCall Smith is a keen observer of life in his home city, Edinburgh, which he's now used in two series, The Sunday Philosophy Club and 44 Scotland Street, a daily 1,000-word serial in The Scotsman newspaper. 44 Scotland Street was released as a book in March and his second serial for the paper, Espresso Tales, will be published as a book in October. The story revolves around the comings and goings at a fictitious building in a real street in Edinburgh. With its multiple- occupancy flats, Scotland Street is in an interesting corner of the New Town, verging on the Bohemian, where haute bourgeoisie rub shoulders with members of the intelligentsia and students. The daily stories focus on the little moral dilemmas of everyday life and the characters' struggles to resolve them. Asked about his ability to give a strong sense of place to his novels, he says the key is 'to use a very light brush and just to give little hints and descriptions, and people will do the rest. I tend not to sit there and describe in great length, rather it's an impressionistic view'. McCall Smith says he was inspired to write the series by the American writer Armistead Maupin, who created the popular Tales of the City as a serial in The San Francisco Chronicle. After lamenting that newspapers no longer ran serialised fiction, McCall Smith was offered a chance at The Scotsman. The third series of 44 Scotland Street will begin in the newspaper tomorrow. 'I was actually writing an episode in the plane,' he says. 'I'm on episode 35 and I want to be at 40 by the time we start. By the end we'll have 110 episodes.' McCall Smith says he's a bit of a serial writer. 'Writing a series is tremendous fun, it gives you a much more real universe in which you can carry on. You obviously get to know the characters and you really don't want to say goodbye.' He says he's committed to writing eight books at least for the No 1 Detective Agency series. McCall Smith says he's lucky he can write nearly anywhere, as long as he has his computer. 'It's almost like getting into a trance,' he says. 'I become unaware of my surroundings and I can write very quickly. I'm lucky in that respect - about 1,000 words an hour when I get going.' He says he makes virtually no corrections. After he finishes Blue Shoes and Happiness, he'll begin writing the next Sunday Philosophy Club novel in December. And what does the future hold for Isabel? 'She's not going to get married. People keep on telling me she should have an affair with Jamie, but it's not going to happen.' With a laugh, he says he hopes to finish the next instalment by the end of February - 'which will make my publisher very happy'.