Two South African women sit on opposite sides of the world, one in a grey north London office crowded with overflowing shelves and filing cabinets, the other on a train in a tiny, dusty station in the middle of the baking veld.

They are strongly linked. The woman in London is Ethel de Keyser, who runs the Canon Collins Educational Trust, a charity which funds southern African students through postgraduate courses both in their own countries and here in Britain - on the understanding that they plough their knowledge back into their homeland.

The woman in South Africa is Lillian Cingo, a star pupil of the Trust. It supported her through a masters degree in counselling psychology at the Tavistock Clinic, and now she manages the Phelophepa Train, which travels to the remotest corners of South Africa with a team of doctors, dentists, optometrists, psychotherapists and specialists in HIV/AIDS. Also on board is an Edu-Clinic, largely funded by the trust, which teaches basic health care to the local communities.

"Some of the problems are solved so easily," Lillian explains when I phone her on the train, presently situated at the small settlement of Tshiame in the Orange Free State. "For instance, in these rural areas, it is the custom to circumcise the boys when they're in their teens. Now these boys, they've already visited the towns, and maybe they've had sex there. Yet when it came to their circumcision ceremony the ingcibi [traditional surgeon] was using the same blade on boy after boy. You couldn't spread HIV/AIDS more effectively if you tried. Through our Edu-Clinic we have persuaded the ingcibis to use a new blade each time, and the results show an immediate drop in infection. It's so simple. It's just education."

When you meet Lillian in the flesh, as I do when she comes to London, you encounter an immensely comforting presence, a big bespectacled Xhosa lady, quick to laugh, strikingly modest. Today, speaking to her on the phone, when she's on her train, her own territory, I hear a different voice - passionate, urgent, almost angry. "Outsiders say to us, 'You've been free for nine years now, why aren't things better?' They don't realise how poor our education system was under the old regime. Even our teachers were under-educated, even our leaders, those in high positions now. People have forgotten this was a nation almost completely destroyed by the former government. We're trying to rebuild it now - but the world mustn't get impatient with South Africa."

As apartheid fell, South Africa revealed itself to be a breeding ground for heroes. I mean the term in its truest, old-fashioned sense - individuals who battle overwhelming odds to triumph in the cause of decency and fairness, and whose own ego seems subservient to the greater good. There are of course the famous examples - such as Mandela and Tutu - but there are also the others, the unsung heroes, and I would certainly number Lillian Cingo and Ethel de Keyser among them. The two are rather similar - both fight shy of personal publicity (it wasn't easy trying to interview them for this article), and both are selfless and tireless workaholics.

"When did you last have a holiday?" I ask Ethel in the Canon Collins offices just off Essex Road. Born, like me, in Cape Town, Ethel resembles all the Jewish matriarchs of my South African youth: a small, dynamic figure, armed with darkly tinted glasses, a powerhouse of information (whether about family gossip or potential fundraisers, the impetus strikes me as similar), a forceful and articulate character. Yet my simple question has completely stumped her. She picks up the phone and dials through to one of her colleagues: "Dora, when did I last have a holiday?" After listening attentively, Ethel reports back to me: "It was in '99. I went to Cyprus. During the week we close over Christmas. Before that... no idea. But anyway, let me tell you about our partnership arrangements, our work on HIV/AIDS, and of course our..."

By the time I leave, my arms are laden with books, pamphlets and videotapes. Although I've been working with Ethel on and off for years, and helped produce two big fundraising galas, I've never fully understood how her organisation came into being. As I talk to some of its veterans now and meet some of its current students, I'm astonished. Theirs is an inspiring and outrageous story, a story of espionage and intrigue, and it all stems from one extraordinary Englishman, Canon John Collins.

His official job was as canon of St Paul's Cathedral from 1949 to 1981. But Collins was one of those churchmen who apply their calling directly to the world they're living in, vividly and fearlessly, and not just to the ancient teachings of the Bible. Tall, gangly, pipe-smoking, with a beaming smile, he emerges in photographs as a vaguely eccentric, almost comic, character - the vicar, maybe, in some 1950s play. In reality he was a formidable figure, a true visionary. During his lifetime he founded Christian Action ("with the object of relating Christianity to economic, social and political life"), helped to co-found CND, and founded IDAF, the International Defence and Aid Fund for Southern Africa. This last was created to assist victims of apartheid. Banned by the South African government, it was initially run from the basement of Collins' London home - the wonderfully named No 2 Amen Court - and it became his most remarkable and dangerous enterprise.

With secret rendezvous in the pews of St Paul's itself, with the creation of dummy trusts and safe houses, and with the recruitment of private individuals as penpals for South African families in need, Collins found ways to smuggle a staggering total of £100,000,000 into the country. His fund paid the defence costs for most of the famous legal cases under apartheid, including the treason trial in 1956, the Rivonia trial (Mandela's trial) in 1960, and the Biko inquest in 1977.

No one could stop Collins. One of the old South Africa's most notorious figures, the master spy Craig Williamson, has gone on record admitting that Defence and Aid was "impervious to infiltration." But opposition to Collins' heroic endeavours came not just from the southern hemisphere, but also the British establishment and the church. During this time, he was variously described as a devil priest, a holy crook, and perhaps most misleading of all, a communist. Death threats and hate mail became a regular feature of life for him and his wife Diana. She has written a book about their marriage, Partners in Protest, which I found uplifting and moving to read.

Defence and Aid sought to help political prisoners fight their cases, but since these often resulted in long prison sentences or even the death penalty, the fund also committed itself to supporting their families. This included schooling the children and sponsoring their further education abroad. In the old South Africa it was extremely difficult for blacks to gain university degrees. The man known as the architect of apartheid, Hendrik Verwoerd, was at his subtlest and most sinister when it came to black education: limit it, he believed, and you automatically create a nation of slaves.

In 1981 Ethel was appointed director of British Defence and Aid. She had already spent the previous decade running the Anti-Apartheid Movement here. Because of its complicated and clandestine nature, Defence and Aid could never qualify as a charity, so Ethel immediately created one - focused specifically on education.

When Collins died a year later, she suggested this new venture be named the Canon Collins Educational Trust for Southern Africa. And when Defence and Aid was made dormant after South Africa's first democratic elections in 1994, the trust became her only responsibility.

She's aided by a dedicated team of seven, five of whom are full-time. And their work is growing all the time. Boosted by the new Nelson Mandela scholarship programme, they're supporting a record number of students this year: 300 in southern Africa and 100 in Britain.

I wonder how much the trust's current beneficiaries know of its amazing history. When I ask one of them, Amos Hadebe, who's doing an MSc in IT management at the London School of Economics, he says he has looked it up online and breaks into a grin - "Oh, man, that priest who smuggled in all that money!"

Amos is a lean, hip, friendly young man with long dreadlocks and a strong Sotho accent. He tells me about applying for his scholarship. It was early in 2002, and a few months later the call came from London. "I remember it was a Friday... a lady from the Trust was on the other end... she said I'd been accepted... oh, I was so happy, I didn't go to work that day!"

Amos was born in Bloemfontein in 1971. I remark that he's too young to remember the events of 1976. That was the year of the Soweto school-children uprising - when they refused to continue learning Afrikaans, the language of their oppressors - a year which some regard as the beginning of the end for the old South Africa.

To my surprise, Amos replies that he remembers 1976 well. By then he was living with his grandfather, who was a policeman. One day Amos returned from school to find their house was gone. It had been petrol-bombed by activists. He says his overwhelming feeling was the same as his grandfather's - confusion. "Even at that age I knew black policemen were hated in their community, but grandad was called a 'nice cop'. He tried to look after political prisoners. He thought he was helping the struggle in his own way."

For Amos it was an early lesson in the complex evils of apartheid. Later, at university, he became politically active himself and is currently the anti-racism officer of LSE's student union, fighting growing Islamophobia and trying to calm tension between Israeli and Palestinian students.

He outlines some plans for the future when he returns home. He wants to set up a digital village in Soweto, getting private companies to contribute the machinery and software, and the government to provide the internet systems. By training the community to be computer literate, he believes they can combat poverty, apply for better jobs and change their lives. It sounds impressive, but how will he persuade sponsors to back him? He gives a big smile: "Well, you know something - I think the initials LSE are going to look quite good on my CV!"

Carmen Hickers agrees. She's also at LSE, studying for an MSc in personnel management. "Unemployment is rocketing in South Africa," she says. "You can graduate with a really decent degree and still be out of work. But with a credit from a top London university... well, I'm hopeful." Carmen is a bright, gentle 24-year-old from Johannesburg, of mixed race, her hair long and red. She's funded by a partnership deal between the trust, the foreign office and Atlantic Philanthropies. As part of her scholarship contract, she will have to lecture at Witwatersrand University in Johannesburg when she goes back to South Africa. "But eventually I want to hit the corporate environment," she says. "That's my ultimate goal."

As we chat in the Brunch Bowl canteen at LSE, and as she relates her story of leaving home and coming to London, I find myself unexpectedly moved. I went through the same disorienting experiences back in 1968 when I arrived here to study drama. Carmen could be myself aged 19 when she says: "London is so anonymous, I can't really define myself. At times it is almost like an out-of-body experience. And the weather!" She gives a little laugh of disbelief. "On the other hand, it snowed the other day, and I have never seen snow before. My neighbourhood is quite ordinary, but covered in snow it suddenly looked so beautiful.

I can relate to Carmen and Amos' personal feeling much more than to their chosen subjects: business and technology. So it's a relief to travel to The Place in King's Cross and meet an arts student: Nkosinathi Mncube, doing a postgraduate performance dance course, co-funded by the trust and the mining company, Rio Tinto. Aged 26, Nkosinathi has a round radiant face - he looks like a black Renaissance angel, presently swathed in layers of clothes to protect him from the London cold.

He was brought up in the small village of Kwa-Ndebele near Pretoria. "My family weren't into this art thing," he explains, and mimics their suspicious looks. "My mother, she said, 'OK, you can do dance as an extra-mural thing, but you must get yourself a proper job!'" His mother was happy to see herself proved wrong. Sadly she died last year, but by then Nkosinathi had already achieved considerable professional success in South Africa, winning two of their prestigious Vita awards, as most promising young male dancer and most promising young male choreographer.

So why carry on studying? He answers passionately: "I'm fascinated by the notion of developing yourself as far as you can go. I mean, at the moment here at The Place we're rehearsing a show with three different choreographers, from Spain, France and here. I have this idea growing in my head - a crossover between African and European dance. This is what I want to take back home."

The trust is not exclusively aimed at South African students, Its title states that it encompasses "southern Africa". The fourth beneficiary I meet is from one of the other countries. His story is the most dramatic by far - protest and arrest in his homeland, an application for political asylum over here - but even as he finishes talking, we both realise I can't print any of it. His family still live back at home and could be endangered. I tear up the interview. His shoulders relax and he smiles for the first time.

I feel quite shaken by the encounter. It was so familiar from the bad old days under apartheid's regime of suppression, censorship and terror. South Africa may be free now, but the surrounding region remains volatile and unpredictable. I hope the services of Defence and Aid won't be needed again. The spirit of "that priest who smuggled in all that money" should be allowed to rest in peace now. His original achievement was remarkable and the charity that continues in his name, the Canon Collins Educational Trust, is doing something equally remarkable - it is literally building the future. My prayer is this: may the future be a safe place to go.

This article was published in the Guardian Education on Tuesday March 18 2003 and is reproduced here with the kind permission of the author.