If there is still such a thing as ‘appointment television’ in this multi-channel age, The No 1 Ladies’ Detective Agency is it. The adaptation of Alexander McCall Smith’s much- loved novel arrives on the small screen this fortnight thanks to a wealth of high-profile talent, most notably Anthony Minghella, who steered The English Patient and The Talented Mr Ripley to Academy Award-winning success, and Richard Curtis, the writer behind such smash hit romantic comedies as Four Weddings and a Funeral and Notting Hill.

With the credits reading like a roll call of distinguished names in the world of cinema and television, and a prime slot on BBC1 over the Easter Bank Holiday weekend, the tale of Mma Precious Ramotswe, Botswana’s first female private detective, known for her traditional build, homespun wisdom and penchant for bush tea, was always going to be one of the shining highlights of the Beeb’s spring schedules.

But is the journey from page to screen ever really effortless? While an adaptation of a phenomenally successful novel could justifiably expect a ready-made audience, the filmmakers carry a hefty burden of responsibility to ensure that the screen incarnation lives up to its viewers’ high expectations.

‘There’s a certain trepidation about adapting such a popular book,’ says No 1 Ladies’ producer Timothy Bricknell, who previously collaborated with Minghella on Cold Mountain. ‘You have to find a way to please the existing fans as well as bringing in new audiences.’

It’s now a decade since the small Edinburgh publishing house Polygon released McCall Smith’s tale in a limited print run. At the time, the publishers understandably felt that a gentle, slow-paced story about a portly Botswana gumshoe, given to pondering cases of marital infidelity, small-scale insurance scams and missing cows in the shade of an acacia tree, might only enjoy a modest appeal. To the surprise of all concerned expectations were exceeded. English language sales of the eight No 1 Ladies’ Detective Agency novels have now topped ten million, while the series has been translated into 34 languages.

One of the series’ many fans was Anthony Minghella, who had been recruited to write a line of blurb for the book’s jacket when it was released in paperback. The book had been optioned for film for several years before the hugely in-demand Minghella reached a break in his schedule and realised he just couldn’t let anyone else take on the challenge of bringing to life the detective agency at the foot of the Kgale Hill in Gaborone.

While McCall Smith passed up the opportunity to work on the screenplay, the author was happy to offer his advice on several key technical aspects of the production.

‘I read the script and made a couple of comments and I went out to Botswana and watched a couple of days’ filming,’ he says. ‘But I always felt the film was in very safe hands with Minghella and Richard Curtis. I have to say I was very impressed by the attention to cultural detail and location in the scenes I saw being made.’

The film employed international casting agents to recruit the actors who would portray such well-loved characters as Mr JLB Matekoni, the proprietor of Speedy Motors, who becomes Mma Ramotswe’s fiancé (played by Lucian Msamati), and Mma Grace Makutsi, the Agency’s meticulous secretary, who is played by Dreamgirls’ Anika Noni Rose. Yet, it was the process of seeking out the actress who would play the central character that almost derailed the entire production.

‘I used to get lots of approaches from people saying they would make the perfect Mma Ramotswe; people wrote letters and enclosed photographs,’ laughs McCall Smith. ‘But I believe the casting of the film was very difficult – Minghella had almost given up in fact.’

‘It’s one of the most challenging castings I’ve ever done,’ agrees Bricknell. ‘Mma Ramotswe is a very iconic character, and we knew we had to find a middle-aged actress of traditional build, not some skinny starlet. We started off seeing Botswanan women and gradually extended our search into South Africa, Uganda and other African countries before heading for London and Los Angeles.’

The American Grammy Award-winning jazz singer, songwriter and poet Jill Scott had tested for the role and had reached the shortlist, though there were some concerns that her relative lack of acting experience would make it a tall order for her to carry an entire feature film. It was only when Minghella came across a series of YouTube clips of Scott’s musical and poetry performances that the director fully appreciated her rare screen presence.

With barely a fortnight to go before the project had to be set in motion or abandoned altogether, the producers decided to go with their gut instincts and cast Scott, who gained weight for the role. Luckily their faith was justified: her performance effortlessly captures the blend of wisdom, compassion and understated humour that has made Precious Ramotswe such a popular creation.

As the first feature film made entirely in Botswana, the producers relied heavily on their local crew for advice on local flora and fauna. The production was not without its setbacks: ten feet-high electrified fences had to be built around most of the sets to protect the cast and crew from attack by wild animals. Despite such tribulations, in a recent interview Minghella described his involvement with the project as being ‘a slow process of seduction, mostly by Botswana itself.’

While the final verdict on the adaptation won’t be known until after its ratings have been recorded and the review cuttings assembled, the film’s quietly confident producers have signed a ten-year lease for the area at the foot of the Kgale Hill in Gaborone, site of Precious Ramotswe’s storefront detective agency. It’s likely then, that the subsequent novels in the series will make the same transition from page to screen. This adaptation certainly makes a refreshing change from the endless English country house mysteries and gritty urban thrillers that currently clutter the schedules. Yet, as Timothy Bricknell points out, while primarily a colourful, funny, entertaining slice of bank holiday entertainment, The No 1 Ladies’ Detective Agency also offers a rare opportunity to showcase a modern, relatively prosperous African nation before a large television audience.

‘People have talked about the responsibility of doing justice to Alexander McCall Smith’s novel,’ he says. ‘But with this production, we also felt a strong sense of responsibility as white people making the first motion picture filmed entirely in Botswana, and presenting modern Botswana to the rest of the world.’

The No 1 Ladies’ Detective Agency is on BBC1, Mon 24 Mar, time tbc.