Botswana is a country blessed with many resources, but, until last year, these did not include a film industry.

In truth, the Batswana, as Botswanans are known, had never needed one - since independence from Britain in 1966, their country has been a quiet African success story, with a solid democracy, founded on tribal principles, and a stable economy. The Batswana have diamond reserves - they have no need for celluloid.

Alexander McCall Smith’s books about a “traditionally built” Botswanan woman who takes it upon herself to open a detective agency in the capital, Gaborone, have changed that. First published in 1998, the stories proved so evocative of a country and a people with a quiet dignity, a moral compass and a sprightly sense of humour that the tales of Precious Ramotswe, her finicky assistant, Makutsi, and her mannered suitor, JLB Matekoni, have become as popular as Rebus or Miss Marple, with fans in 40 countries.

Those fans included Anthony Minghella, Oscar-winning director of The English Patient, and Richard Curtis, writer of just about everything that has defined modern British screen comedy in the eyes of the world. Both loved not only the books, but their depiction of a different Africa from the roiling continent of civil wars and starvation that dominates the western imagination. Minghella had collaborated with Curtis on Comic Relief, directing short films, and they had often talked about working together since they shared offices when Curtis was writing Four Weddings and a Funeral. This idea crystallised in 2001, when Minghella’s production company, Mirage, acquired the rights to The No 1 Ladies Detective Agency, but it still took six years to get a script together, with both men signed up to projects ranging from Cold Mountain to Love Actually.

Even once they began e-mailing drafts back and forth in 2006 (with Curtis finessing the Ramotswe/ Makutsi patter over their endless cups of bush tea, while Minghella tried to ground Mma Ramotswe in a credible psychological reality), it was unclear whether their adaptation would be for television or cinema. The BBC and HBO came on board as UK and US distributors, with the idea that a feature-length film might spawn a series, but, even with the additional financial clout of the Weinstein Company, the production found itself short by $5m.

There was also the small matter of where it might be filmed. As the producer Tim Bricknell says: “It was always the ideal situation to shoot in Botswana, but the economic divide between shooting there and in South Africa was huge. There was no infrastructure in Botswana, no film crew, no equipment - that’s all expensive.”

They approached the Botswanan government, saying they wanted to film there not only because The No 1 Ladies Detective Agency was set there, but because the books were culturally important for the country - there had already been an influx of tourists asking taxi drivers to take them to JLB Matekoni’s Speedy Motors garage or Mma Ramotswe’s house on Zebra Drive. It was gently suggested that it might want to ink in some incentives, much like the tax rebates offered by South Africa to visiting film crews. With barely a flicker, the Botswanan government made up the $5m shortfall. “If we had gone somewhere else, we would have ripped the heart out of the project,” says Bricknell’s fellow producer Amy Moore. “The Batswana are especially proud of this character, Mma Ramotswe. She has become iconic.”

Yet an iconic literary character always makes for controversial casting. Millions of readers have different mental images of the redoubtable Mma Ramotswe - even McCall Smith admits that he never held a specific face in his mind’s eye. Now Minghella had to find one. “Anthony was almost at his wits’ end,” says Curtis - until Minghella auditioned the Grammy-winning American soul singer Jill Scott. It was as if she had walked right out of the book, Minghella recalls. “She has all the qualities: she’s a big, gorgeous woman; she’s intelligent, romantic, funny, powerful. She had to stretch herself far beyond anything asked of her before. But it’s worth it. She’s magnificent. We all fall in love with her.”

Around her, a starry cast was assembled (including Dreamgirls’ Anika Noni Rose, David Oyelowo and Colin Salmon), but the bulk of the supporting cast and crew, including Kudrah Alabi as the young Precious, came from the country that also provided the backdrops, the culture and the aesthetic. “We involved about 1,500 locals - as extras, but also in small parts, and in every department,” Bricknell says. “We had assistants and an internship programme set up to train local crew. It was important to the government that we did that, but it was also common sense. Anthony and I have been working on this for a long time; in the end, though, we are two white guys from London. We needed the local people because we didn’t know anything about the country.”

Almost all of McCall Smith’s stories have happy endings, and so, it would appear, does this one. Last week, the BBC and HBO announced that, on the back of the first film, a 13-part series of hour-long episodes has been commissioned for shooting this summer. “Anthony will control the story lines and script, and I hope Richard will oversee the scripts,” Bricknell says. “Anthony and Richard don’t plan to write any in the first season - but, as things go on, maybe that will change. They may come back to write a special - they may even direct again. It’s something they’re both committed to.” And as for Botswana’s No 1 film-production industry? “We will continue to use our local actors and continue to grow the talent base there.”

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