A vehicle rolls through the grasslands of Africa, stirring up a cloud of dust.
As soon as the wheels stop, it is besieged by children hungry for the special cargo – books.
The chant goes up from the children, "One book! One book!"
On board is another special resource: volunteers, who help the words inside those books come alive for the eager young minds.
This is a Book Bus in action, made possible by a modest office 5,000 miles away in the cooler and lusher landscape of the Tamar Valley.
The South West connections extend beyond the Book Bus logistics base in Tavistock, which recruits volunteers and runs the travel arrangements for those who serve on the three vehicles in Zambia and Malawi in southern Africa and Ecuador, South America.
The region supplies volunteers who pay their own way and give up their time to serve as reading helpers for two weeks on one of the buses.
They are changing lives by helping children to learn to read and to understand the power of books to improve their lives.
The help is greatly needed. Many of the children come from illiterate households in extremely poor countries. Malawi is the eighth poorest country in the world, and Zambia the 25th most impoverished out of the 180 nations ranked by the World Bank.
Change happens both ways, though. "It is a fantastic experience," says Plymouth-born teacher Jo Houghton, 25, who did a stint in Zambia.
"The children were just adorable. I've got the bug. I'm arranging to go back."
The small charity with a big impact got a royal seal of approval recently when Princess Anne visited a Book Bus at Victoria Falls as part of her official trip to Zambia.
That's a sign of the progress made by the mobile-libraries-cum-literacy-centres in five short years.
In 2007 Tom Maschler, head of publishers Jonathan Cape, started with a bold idea. An unlikely chain of events followed involving an old London bus, a yoga teacher and an adventure tour operator.
Tom was retiring and leaving a legacy in the literary world: he founded the Booker Prize, one of the leading literary fiction awards. Now he wanted to leave something behind in the illiteracy world. He had been to Zambia and wanted to start a project there. He bought a vintage London bus, a 30-year-old Leyland Tiger, thinking that the vehicle would be ideal as a mobile library.
But there was a glaring problem. "He hadn't thought through the logistics of how this could be done," says Mark Davison, secretary of Book Bus.
"But his yoga teacher, Jackie, happened to be the girlfriend of David Gordon, my partner in an adventure company."
Mark and David had all the expertise needed to make things happen. They had set up specialist overland and safari travel operator VentureCo in 1999 after both worked in other companies in the sector for decades.
The company, then based in the Midlands, now in Tavistock, became the Book Bus project partner and wheels started rolling.
Quentin Blake, illustrator of the Roald Dahl books, decorated the bus in his distinctive style, Tom's publishing contacts and friends donated books and money, and the bus arrived in Zambia in 2008.
Its base is Livingstone, within reach of poor communities, which can most benefit from its services, and close to Victoria Falls, the Zambezi river and a national park rich in wildlife – all strong attractions for volunteers who can also see some of the greatest sights in southern Africa.
The original vehicle "died" last year but Book Bus lives on and has spread to cover the neighbouring country of Malawi and make inroads on another continent in Ecuador, where the reading language is Spanish rather than the English of Africa.
That first vehicle was hardly built for the rigours of Third World roads. "It was a proper London bus with clearance of only a few inches," says Mark. The new buses are more robust while the vehicle in Ecuador is a specially kitted out lorry with a smaller wheelbase, higher clearance and larger engine to cope with the mountainous terrain. All have been decorated with unique illustrations by Quentin Blake.
Next April Book Bus will roll into India and Nepal for a pilot project, which the charity hopes will become a permanent presence taking the number of countries covered to five.
As the project has grown, so has the number of books. The publishing industry provided 37,000 last year. So the project does not want donations of books.
Financial contributions are welcome as are new volunteers, who pay their way – typically about £1,500 for a fortnight including flights – and enjoy comfortable safari-style tented accommodation, including a swimming pool, for their weekends and evenings off.
Mark says: "We welcome aboard individuals, friends, couples and active families. Previous volunteers' backgrounds have ranged from teachers to a banker, plumbers, lawyers and even a shepherd and his wife."
His fellow VentureCo worker, Seth Harris, adds: "We get a lot of early retirees, many from a teaching background.
"We've had quite a few repeat volunteers."
The children are generally of primary school age. Each is given a book on condition that they bring it back and swap it for one which a friend has been given. That gets them used to the idea of a library, which is set up for the school.
The volunteers aren't teaching the children to read. The aim is to help and encourage those who would otherwise have little or no access to books. Reading and storytelling creates and inspires, getting children interested in learning.
As one volunteer reports: "The favourite chant (from children) was 'One book! One book!'. The shouts got more adventurous as the week went on, 'one book of colouring', 'one book of lions' and at the end of the week we gave all the children their own book to take home. They were thrilled."
Mark has experienced the magic first-hand. "The enthusiasm knocks you off your feet," he says.
"From the first thing on Monday morning when you start, through to the end of the week with them. The thirst for literacy is so strong."
Seth, who visited Zambia in 2009, adds: "It blows you away, the receptiveness, the responsiveness of the children." Many volunteers, too, are swept away by the enthusiasm. "They do four hours a day in school, which gives them the afternoon free," says Seth. "But many volunteers do more and spend some of their free time planning for the next day."
With class sizes in African schools running at up to 150, and some children taught in shifts because of a shortage of teachers and funds, every bit of extra help from outside is effective, particularly working in small groups. "A teacher in this country will tell you that they get 12 or 13 minutes each day one-on-one with each child in their class," says Mark. "In Africa that one-on-one time is a matter of seconds."
Jo, who now teaches at a primary school at Whitstone, near Bude in Cornwall, agrees. "Without a doubt it makes a difference," she says of her experience with Book Bus in Zambia in 2009. "You see it in the children's reaction.
"You are working with a group of nine or ten and are just surrounded by children from the rest of the school who can't wait for their turn. Everybody just wants to read and to get involved with Book Bus.
"These small things make a difference. Since I came back I can't stop thinking about it. I'm not one for lying on a beach in the sun. I like doing things." She plans to join Book Bus again next spring in India/Nepal.
Another Plymouth teacher who has signed up for Book Bus can't wait to get involved.
"It fits my idea of engaging children in learning and getting them excited," says Jane Downing, 29, who will be going to Malawi in November.
The special needs supply teacher who lives in Tavistock says she likes doing something "useful" on a break and is not put off by the £1,500 cost. "I am very lucky to have the life that I do. I am very privileged to be able to help. I sound a right do-gooder, don't I?" she adds, laughing.
What about the argument that the typical £1,500 that the volunteers spend on their break with Book Bus might do more good if directed straight into a development charity?
"Volunteers can see the difference they are making," says Mark. "I think we compare favourably with any development charity. Nobody working for us flies club class and we don't have brand-new 4x4s."
Overheads are kept to the minimum. Locals are employed as drivers and UK nationals are used only in the essential role of project co-ordinators on the ground.
Mark adds: "These person-to-person interactions are so strong. Who knows what the child you are helping will go on to be? They could be the next town councillor, they could be president of the country one day."