A hard lesson: James Nesbitt on the child victims of Aids in Africa - and what they taught him

The second is my own daughter, home in London. Two Margarets, born thousands of miles from each other, but living worlds apart. And it is because I have a daughter christened Margaret (although we call her Peggy) that her story affects me more than the others I encountered during my trip to Zambia with Unicef, visiting projects aimed at countering the effect of the HIV/Aids pandemic on education.

The story of Margaret seems to sum up the HIV/Aids crisis facing Zambia. Three of her siblings do not go to school either, missing out on vital HIV/Aids education. Since their father died, the family has faced huge financial difficulties: the older ones cannot afford to go on to secondary school.

Shy at first, Margaret gains confidence and speaks in English, fluently and articulately. She has a tumour on her left ear which should require immediate attention but here, is the least of her worries. She tells me how sad leaving school made her. As an accountant, she would have been able to give money to her mother. She also wants to be a nun because she admires their moral strength and does not trust boys.

We go inside her house. There are two rooms for eight people. Every morning after sweeping - cleanliness is very important - she makes porridge. She starts to demonstrate but I tell her not to waste food. She seems hurt. On the wall is a faded photograph of her with her father. I ask her if she misses him. Because of the huge numbers dying and Aids affecting every family it is often easy to forget the emotional loss. Margaret looks at me and speaks steadily: "Very much." I ask: "What are your biggest fears?" She replies: "What we will do when Mam dies." All the while her mother looks on, not understanding, seemingly proud of her girl but embarrassed, knowing why these foreigners are in her house.

Outside, Margaret's siblings eagerly line up. I ask them what they want to do. It is heartbreaking. The youngest wants to be a nurse "to make all the sick people better". Thomas wants to be a lawyer, "to defend the poor". There is a teacher, another accountant and one even wants to be a music producer. The remaining boy wants to be a doctor, "to stop HIV/Aids". He was born on New Year's Day and his parents christened him Lucky.

It is impossible not to feel angry. In the UK, these children would finish school, go to college, and have a real chance of fulfilling their dreams. Margaret and I play hopscotch, but then it is time to go. This magnificent 17-year-old girl shakes my hand and thanks me for coming. As I head for the hotel, she returns to her chores and her sick mother.

There is much that should unite these two Margarets. All children want to feel secure, to be looked after, to be fed and cuddled. They want to be confident enough to go to school, so they can learn, make friends and enjoy their childhood safe in the knowledge they can return home to the loving arms of their parents.

More than anything, as parents, we want our children to be healthy. My nightmare is that I outlive Peggy or die when she is young, robbing her of a dad and me of watching her grow. I want her to love and respect me, but do not mind if she is a bit embarrassed by me. I want to struggle with her maths homework but be the dad who teaches her the recorder or how to drive.

I will force her to go to Old Trafford, even though she hates football. I will want her to stay with me for ever, but I know that one day she will go. I want her to know she is loved. I am lucky. I have at least a chance of having all this. Margaret's father did not. Unable to work and with mind and body deteriorating, all he could do was watch his beloved daughter watch her beloved dad die. I know that our Peggy has everything she could wish for, and takes for granted that her parents are there, that they love her and that she never has to worry about where the next meal is coming from.

In Zambia, Margaret has not a hope. Born in the wrong place at the wrong time, she is among 20,000 youngsters heading households, watching their childhood slip away. I slept badly that night. Aids has orphaned more than 500,000 children in Zambia, robbing them of their childhood and futures.

A Unicef briefing makes clear a dangerous cycle is setting in: more HIV, less education, more HIV. Unicef's response, under the slogan "Unite for Children Unite Against Aids", is known as the four Ps:

* Prevent mother-to-child transmission of HIV;

* Provide paediatric treatment;

* Prevent infection among adolescents and young people; and

* Protect and support children affected by HIV and Aids.

My interest in educational projects is because my father was my inspirational primary school headmaster, my three older sisters are all teachers and I even considered entering the profession, before acting took hold.

Margaret's former school, the Chipata Open Community School, was set up to cope with the hundreds of vulnerable local children. Among 950 pupils between nine and 16, there are 500 orphaned, largely due to Aids.

Again, despair mingles with hope. I talk to Zelipa, 34, a teacher, who last year tested HIV-positive, enrolled into the anti-retroviral therapy programme and is now well enough to return to teaching. Stigma prevents her from admitting her illness, apart from to the headmistress, but courage makes her educate her class about HIV/Aids prevention.

Break-time at 10am brings, for many children, their only hot meal of the day. Porridge is distributed from huge industrial bins, an incentive to some to go to school. Once there, their appetite for learning and playing takes hold. But the school can enrol only a third of the vulnerable local children.

The headmistress, Elina Daka, has five children but also cares for her niece, Thelma, whose parents died from Aids. Thelma is also HIV-positive. She is 14 but looks eight and even after gentle coaxing from her aunt, says nothing. Thelma is several grades behind. The free drugs have given her a chance of life, but who knows what trauma lies within.

At the Kalingalinga clinic, staring faces wait in line for such drugs which, for a while, allow them our basic right to live. In makeshift wards, sick children lie on makeshift beds watched over by sick parents. These are the lucky ones. Only 5 per cent of all children with HIV have access to life-preserving drugs. It is staggering. The other 95 per cent will die before they are five.

Finally, we visit the City of Hope Community School, where more than half of the 700 children are orphans. Behind imposing walls, City of Hope is a green and tranquil haven of happiness. Stone circular classrooms sit among trees and grassy play areas. The children are encouraged to climb a huge oak called the Vision Tree, so they may be alone to think. I go up with Paul, who is six, and for the first time, feel happy. We look out over the vegetable plots, the field of maize and the chicken-run.

This is a model for what could be achieved with more resources. Here, children are allowed to be children. A girls' football match is about to start, but first the pupils put their hands on hearts to sing the national anthem. "We are Zambians, proud and true." Here, at the City of Hope, it is difficult not to believe them.

My head is full of figures. In Zambia, one in six of those aged between 15 and 24 is HIV-positive. Every year, 40,000 babies are born HIV-positive. There are 75,000 street children and, terrifyingly, life expectancy here is only 37.5 years. HIV/Aids is redefining childhood, and Unicef is calling on everyone - from world leaders to ordinary people - to put children at the centre of the global response. If the world does not act now, it will be too late for so many.

Do we have a moral and social responsibility to these children? To the orphans and vulnerable children I met, to the silent and traumatised Thelma, to Paul who sat beside me on the Vision Tree, and to proud, intelligent Margaret, denied a childhood and a future because of this terrible disease. I think we do. We know we do.

To join Unicef's campaign, Unite for Children, Unite Against Aids, log on to www.unicef.org.uk/aids. ITV News will show reports about James Nesbitt's trip at 6.30pm from next Monday to Wednesday.