I first met Joyce Mfolo 40 years ago. I was a boy living in Johannesburg and Joyce, then 18, came to work for my parents as a domestic. Her job was to wash our clothes, scrub the floors and clean the house and, when my parents went out at night, to look after my three younger sisters and me.

It was the Sixties and apartheid affected every facet of our relationship. For example, Joyce would never sit on our sofa or eat with us at our dinner table. This was the way, despite my parents supporting the anti-apartheid Progressive Federal Party. If you had told me then that in the summer of 2008 I would spend four weeks building Joyce the house of her dreams, I would have laughed in disbelief.

I grew up knowing little about Joyce, not even her surname. But she had a brilliant sense of humour and could make light even of serious things: like when the police came demanding she produce her "pass book" and my parents hid her in my cupboard and sent the police packing with a bottle of whiskey (the law required black people to have a "pass" to live in the city and Joyce, who grew up in a rural area, had been denied one).

In time Joyce became a part of the family, often jokingly referring to herself as Joyce Cohen, though it would be years before I would hear her personal story. I had no idea that as the eldest of nine children she'd been abandoned by her parents to be brought up by her grandparents, that she prided herself on being "their favourite of 54 grandchildren", or that the greatest sadness of her life was that she'd missed her grandfather's funeral because he died while she was "on holiday" with our family, looking after us children.

For the first 25 years of her employment, Joyce lived in our backyard in a concrete room with a freestanding galvanised iron tub for a bath, which was in line, I am ashamed to say, with the standard accommodation of domestic workers. She got married and divorced and had a daughter called Margi, who later had three children of her own: Lebo, Brigitte and Hendrik.

By the mid-Eighties, I had joined the United Democratic Front (the internal ANC) and as the country began to change, Joyce's lot improved, too. My parents built her comfortable en-suite new quarters and funded Lebo's education.

By then I was starting my own family with my wife, Pam. Without meaning to, Joyce and I became friends, often shooting the breeze in her bedroom where she kept pictures of my daughters alongside her family on the wall.

In 1994 I visited her one weekend at her own home, a stiflingly hot corrugated-iron shack in Hammanskraal, a black township 50 miles north of Johannesburg. As my daughter Jessie, then four, played in the sand with Joyce's grandson Lebo, she told me about her dream to own a house - "a real house made of bricks and mortar" - a dream to which I could relate, living, by then, in a tiny flat in London. 

Over the next decade I got my house in Crouch End and Joyce, having abandoned her shack for a £40 plot on the outskirts of Polokwane, had begun to build hers. Polokwane, a three-hour drive from Johannesburg, is today famous as the place where the African National Congress overthrew Thabo Mbeki as party leader last year in favour of Jacob Zuma and set the country on a new course.

But for Joyce, Polokwane is home, the place to which she'll one day retire, surrounded by her daughter and grandchildren. Every time I visited South Africa, she would tell me about her house. By 2008, she'd built four rough rooms that were neither plumbed nor plastered but the rising cost of bricks meant progress had stalled. "At this rate," she said matter-of-factly, "it will take another 10 years to finish."

One day, it dawned on me that I could help Joyce realise her dream, and this was the right way for our family to show our appreciation for four decades of loyal service. When I broached the idea with Joyce, she couldn't stop laughing. "Oh David, let us pray for that day," she said.

Things moved fast. Michael Hart, an architect friend in Johannesburg, agreed to work for free and came up with an elegant design of an open-plan kitchen, dining room and lounge set around an internal courtyard linking the old house to the new.

Joyce's partner, Silas Mokhabuki, 68, a veteran builder, offered to bring his team of workers at half their normal fee. I set about raising the £10,000 we'd need, half from my savings, the rest from family members and an anonymous City philanthropist.

I took four weeks' leave from the Evening Standard and joined Silas and his builders on site after they had dug the foundations. The day I arrived, I helped to "throw" the concrete base. The next day, my muscles aching from all the heavy lifting, I sat down with Silas to draw up a schedule. He warned me he had never done a house so quickly and that to avoid bottlenecks I needed to have the materials on site in good time. I headed off in his battered old pick-up truck, which, after 569,154 kilometres had no first gear, no horn and a speedometer set on zero, and rattled all the way to Dadas World builders' merchants in the city centre.

When I showed the manager my buying list for the day - 50 bags of cement, 500 bricks, three French-door frames, five window frames and eight lintels - he priced it at £1,200. After I explained the project, he said, "May God give you a long life" and reduced the price by a quarter.

I drove back feeling like the cat that got the cream, only to find Silas pacing anxiously. "It's the water," he explained. "They were supposed to deliver. We cannot build without water." Although the government had begun to lay pipes in this rural part of Polokwane known as Ga Thoka, it would be months before they finished and we had to buy in four drums a day for £10.

In many ways the evolution of Ga Thoka in greater Polokwane exemplifies the prodigious growth in rural black areas of South Africa. Before 1994, the locality comprised just four tin shacks. Today, Ga Thoka has 4,500 residents, many living in brick houses. Its streets are still potholed but it now has electricity and with good jobs available at the nearby University of the North and the £80 million 2010 World Cup football stadium going up a few miles away, everyone is building.

Soon I was joined by my sister Neria, a former film-maker who used to work with Al Pacino and who had flown in from New York to film the project. Every evening, covered in a fine layer of dust, we'd drive to the nearest KFC to use their toilets, wash our faces and clean our teeth. We felt like a couple of poor whites.

Week two began on schedule with the walls shooting up. Silas insisted that the place to get cheap timber was to drive to "the machine in the mountains", Steven's Timber Mill. But the mill could not supply us for weeks, so we diverted to a new operation where Boet, a local preacher turned businessman, agreed to supply us at half the prices in Polokwane.

THIS seemed like a great deal but Boet only delivered a third of the order and when I called to remind him that "as a preacher", surely his word was his bond, he was having none of it. "No, Dave," he said in his thick Afrikaans accent, "for me church and business are totally separate things." It set alarm bells ringing and when we drove up to load what he'd already cut on to our truck, Boet hadn't even started the rest of our order.

"Sometimes cheap is expensive," said Silas ruefully, as we headed off to seek a more reliable supplier.

In week three, my wife Pam arrived with daughter Jessie, 18, and her two friends Adie and Eliot, who had flown in from London to start their gap year in Polokwane. Pam spent her days relaxing on a deckchair in the sun-drenched courtyard, while the gap-year kids plastered walls in the morning and played football with the local children on the dusty road in the afternoon.

Joyce was dying to see the house but we had agreed that she wouldn't visit until we were done. We were racing towards the finish line. I employed an extra team to plaster over the weekend but an allnight drinking session rendered the builders, rather than the walls, plastered.

As D-day approached, the house was substantially up: the tile roof was laid, the windows glazed, the electricals fixed, a bath and toilet ready to be installed and painting under way. We had managed to keep to our £10,000 budget. It would take another fortnight to finish it off but with my parents coming to join us, we were ready for the moment when Joyce would see her new house for the first time.

At 11am on the final morning, Silas drove Joyce to the house. She alighted looking like a queen in a new outfit bought for the occasion. As my family and the builders chanted "welcome", she looped her arm through mine and said: "Come, David." We walked under the porch, through her new front door, and into the hallway.

Oh-le-lo!" Joyce exclaimed, spinning 360 degrees and beaming. For 10 minutes, she walked through the house in a daze. Later, after being presented with the framed plans of the house by my mother and father, she said to me: "For 40 years I have been in your parents' house; today for the first time they have come to see mine. I've got no words, David. I don't know how to thank you for your vision and for what you and your family have done." I had never seen her so happy.

Later, when I drove Joyce deep into the countryside to the office of the homeland chief to pay her £2 annual tribal levy, I asked the chief's clerk, Jack Maake, how much it would cost to buy six adjacent plots in Ga Thoka. "Why do you want to know? Do you want to live here?" he asked, mystified. No, I told him, I'd seen that the children in Ga Thoka had nowhere to play and that maybe we could arrange to sponsor a football pitch, especially with 2010 around the corner.

"That is a brilliant idea!" he said, leaping up from his desk. "In that case, we'll give you the plots for free." We could call it Ga Thoka United FC, I suggested. "No," he shot back, "we will call it the David Cohen Football Stadium." He seemed quite determined. "We don't get many whites in this office. You being here with Joyce means a lot to us - it is proof that the Rainbow Nation is working."

By now Joyce had her head in her hands and couldn't stop laughing. "Oh-le-lo, David! I can't get my head round what has happened here this day, this month, this year. Today a house, tomorrow a football stadium. I think you must like it here in Polokwane."

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