SOMEWHERE in the Liberian city of Tubmanburg, a man named Boakai is whizzing around on his motorbike, dodging potholes and heading for the latest on the long list of schools he visits.

At one point he will pass the offices of an independent radio station, which is run by a man named Meloshe. He's one of the country's media stars: the news director at the station, he sees it as his job to hold the government of President Ellen Johnson Sirleaf to account.

Little connects the man on the bike and the man in the radio station, save for the fact they owe a considerable debt to a small charity based thousands of miles away in Dalmally, Argyll. Years ago, Mary's Meals fed both when they were young and vulnerable. Boakai walked three miles every day to be fed and to attend school. The meals were provided in a leper colony. Today, Boakai works as a monitor for the charity.

From providing meals to 200 children in one Malawian school in 2002, Mary's Meals now feeds 996,926 chronically hungry children every day in Liberia, Malawi and 10 other countries across Africa, Asia, the Caribbean and Latin America. Former child soldiers in Liberia and semi-nomadic children in Kenya are among those whose lives are being changed.

In his memoirs, to be published later this week, the charity's founder, Magnus MacFarlane-Barrow, writes about lots of personal success stories such as Boakai's and Meloshe's - people who might have died of starvation had it not been for the intervention of his charity.

But a vast problem still needs to be addressed. Globally, 57 million children miss school because of poverty. They beg on street corners or trawl through fetid rubbish dumps rather than attend a school. Those who do attend are often so painfully hungry that they cannot focus on what the teacher is saying.

MacFarlane-Barrow, while naturally recognising that much more needs to be done, says his own commitment has never flagged. He certainly puts in the hours, and the long, long flights: he went out to Malawi and back again the previous week, and, as you read this, he is once again making a flying visit to that small but beautiful landlocked country.

"This is a particularly busy spell," he says in the charity's office in Possilpark, Glasgow, the base for its teams handling finance and operations, global communications, programmes and fundraising. "Most of the time I'm at home in Dalmally with my young family [he and his wife Julie have seven children] but I travel a lot. This approaching landmark [of one million children] obviously creates a huge opportunity to raise awareness of the mission, so I'll be travelling pretty much solidly over the next few weeks.

"When the book is published I'll be doing a lot of engagements in the UK and I'll be going to America, where there are a lot of things opening up for us.

"I was over in Donegal for the first time yesterday and meeting these amazing Mary's Meals support groups. I'd never met these people before and there was one amazing story after another on the incredible things people are doing.

"That sort of thing renews my enthusiasm all the time and I suppose that's what I feel like, right from the beginning, from those early days when I went to Bosnia. You can get swept along with this wave and it has never let up. It just kind of builds. I don't feel so much like I'm pushing anything, it's more like I am being swept along by it. It very rarely feels like a burden or a hardship. I love it. Like other things in life, as you get older you get a wee bit more tired, flying around different time zones, but I love it as much as ever."

MacFarlane-Barrow was in his mid-twenties and a fish farmer in Argyll when, in late 1992, he and his brother Fergus organised a local appeal for refugees from the war in Bosnia, their consciences pricked by TV news reports of the conflict. The response was so generous that three weeks later, the brothers and their second-hand Land Rover became part of an aid convoy bound for Medjugorje in Bosnia-Herzegovina.

The donations continued to flood in. MacFarlane-Barrow made more than 20 journeys to Bosnia in the first year. Deliveries were also made to Croatia. A registered charity, Scottish International Relief, was born. In time, SIR took to building homes for abandoned children in Romania and setting up mobile clinics in Liberia, while delivering aid to Croatia and Bosnia-Herzegovina. Julie, the woman who would become his wife, was his co-driver on some of the first deliveries to Bosnia-Herzegovina.

In 2002 Malawi was one of a number of countries in southern Africa affected by a deadly famine. Some districts were hit by floods, others experienced the agonies of dry spells. Whatever the cause, several million people were affected.

When MacFarlane-Barrow went to deliver food he was struck by the overwhelming number of Aids orphans and by the plight of the people. He met a 14-year-old boy, Edward, who said, quite simply, that all he wanted was enough food to eat, and to be able to go to school one day. Edward's words have stayed with the older man for ever.

The actual idea to create an organisation named Mary's Meals that would feed African children in their schools came from Tony Smith, an English businessman who was active in Malawi. He had in turn been inspired by a televised speech by US Senator George McGovern, a long-time advocate for the world's starving people (and, incidentally, the Democrat who lost to Richard Nixon in 1972). Edward's words and Smith's idea came together in MacFarlane-Barrow's mind. SIR established Mary's Meals, with Macfarlane-Barrow and Smith as the first trustees, and a remarkable organisation was born.

"It wasn't my idea at all but it did coincide with everything I had been learning and experiencing up until that point," MacFarlane-Barrow acknowledges. "That was absolutely a moment of: 'Yes. This is what we're supposed to do.'"

To go back briefly to his efforts in Bosnia, did he feel a sense of vocation there?

"I did, though not on day one. I took the first delivery of aid there at the end of 1992 and didn't intend for it to be anything more than that. But when I came home and found the appeal had snowballed I thought, 'Maybe I'll do this for a year.' During that year it grew at such an incredible rate, especially in Glasgow and surrounding areas, that I began thinking, maybe this is what I'm called to do. And that has never gone away.

"So much of what followed was not planned by me. The first 10 years were a whole variety of things and then the Mary's Meals thing landed. I don't think it could have happened without that 10 years of experience of learning things - it really grew out of that."

In Malawi, the charity now works across some 25 per cent of the country's primary schools. The beneficial impact can already be felt.

"Some of the longer-term things will take longer to gather evidence on, but school enrolment has increased, and attendance rates and academic performance have improved hugely. We have made our monitoring and evaluation and data-collection a priority in recent years because we want to prove that this works.

"One of the great things, and the reason I called the final chapter of the book Generation Hope, is that you now have a generation of people leaving school. It's really uplifting to meet these incredible young people who are going to change things in their communities and their countries. There are lots of them, and they say they would not have gone to school if it had not been for Mary's Meals. That longer-term impact is only just beginning."

The work on the ground is done by an army of 65,000 volunteers. "It is having an impact on the nation, yes. People there are very aware of Mary's Meals," MacFarlane-Barrow says. "But that's one of the dilemmas - we're getting requests from all over, lots of different countries, and there is a temptation to say yes and be very thinly spread.

"But it has been really important to concentrate a lot of our resources on one or two countries as our big projects, because then you start getting an idea of the impact it has at a certain scale.

"I suppose it does have, in that sense, a very strong message to the Malawian government and others - that this is possible at scale. We have proved this approach works at a reasonable scale; we can do this in those different environments. I hope that's a challenge to many people outside - if we can do that from a shed in Dalmally, why can't they?"

Liberia has very recently been declared Ebola-free by the World Health Organisation after more than 4,700 deaths, but many serious problems remain.

"It's our biggest country after Malawi, and is a place very dear to my heart. It has suffered in a particular way. We were there during its civil war but I was there before Mary's Meals - that was my first experience of Africa. I've been going there since 1997 and have a lot of old friends there.

"There's probably an even greater need for Mary's Meals there than in Malawi: it's one of the worst countries in the world for numbers of children out of school - only about 50 per cent of the kids ever go to school at all.

"You see dramatic rises on enrolment when you start serving the meals there. Liberia is important for us and we hope to be able to reach more children there.

"Kenya is another wonderful project - two parts of the country up in the far north as well as some more urban settings. South Sudan and Uganda are small projects. Zambia we have just begun; it has a lot of similarities with Malawi."

In his book MacFarlane-Barrow touches not just on the 57 million impoverished children who remain out of school but also the other 66 million who attend school but are unable to learn properly.

In his epilogue, he describes as "a scandal" the fact that millions of children are not fed each day and that thousands starve to death every day. He urges governments and international bodies to devote a tiny fraction of their resources to feed all of Africa's primary-school children.

Does he think the will is there? "I don't know. I'm not clear about why it doesn't happen because I think it is achievable. I understand the point of view of the governments in the countries where we serve meals that they are so under-resourced and have so many difficult choices to make. In education, they don't have enough classrooms or teachers and the budget is stretched across those priorities.

"I do question why 57 million children will be out of school because of hunger. Some of the other goals facing the international community are much harder to achieve. Addressing hunger would be something that they could hold themselves to account for and succeed in."

In the meantime, his efforts continue. He acknowledges, modestly, the OBE he was awarded in 2011, and the fact he was included in Time magazine's 100 most influential people (Gordon Brown, no less, wrote an admiring description of him for the list). And he recalls fondly the fact that his charity has touched people's hearts. "In Donegal they were saying how happy it makes them to be part of a mission, and that is a hallmark of Mary's Meals, wherever I go in the world.

"It puts a smile on people's faces ... there is something about it that makes people happy, and that's one of the reasons I love it."

The donations continue to come in, too. One man arrived in the charity's Oban shop with a donation of £1,200. Marie, the shop manager, asked for his details, so that he could be properly thanked. "You don't need to know my name," he said. "Life's been good to me."

The Shed that Fed a Million Children: The Extraordinary Story of Mary's Meals is published in hardback on Thursday by William Collins, priced £12.99. It will also be available as an ebook. Visit marysmeals.org.uk