Grandmother Geraldine Booker was looking forward to a comfortable retirement when her life was turned upside down by a visit to Uganda.

Inspired by the hope of the people in the midst of poverty and death, she vowed to do what she could to make things better.

Now she and her husband devote their lives to helping orphans in an Aids-ravaged village.

After a year of working with the children of Kabbubu, Geraldine thought she had been through the worst of the emotional turmoil.

But Medina touched her in a new, raw way.

The little girl seized Geraldine's arm with a desperate, hopeful grip.

She looked up at the strange white woman with her huge brown eyes and flashed a heart-stopping grin.

Aged just four and already orphaned by Aids, Medina was dressed in her only outfit - a ragged man's jumper that hung in folds from her bony shoulders.

Long after Geraldine unclasped the girl's dry, dusty hand from her arm, she could still feel her grip on her heart.

With 400 others clamouring for her attention, Geraldine had to stop herself from scooping up this one special child and taking her home. Leaving her behind almost broke the grandmother-of-three's heart.

She said: "The first time I saw Medina, there was a commotion in the village and she was crying in the middle of it all. They said she had run away from home because her grandmother beat her.

"Out there, when you have brought up a huge family and you are destitute anyway, to have to look after another child in your old age can be too much. Medina's grandmother couldn't cope. Sometimes she would hit her.

"She was so little and she looked so distraught. I would have loved to have taken her home with me. Part of me wanted to sneak her into my suitcase and just bring her back.

"I could see she was a lovely child and she had a wonderful, mischievous grin. She was gorgeous but her eyes looked so sad."

Geraldine found a place for Medina at the nearest school and arranged for the headmaster to pick her up and drop her off every day. For a while it looked as though her life was improving.

Then, last November, Geraldine and her husband Geoff received a fax from Uganda. It read, simply: "Your little girl Medina has died."

Geraldine never established the reason for Medina's death. Some said it was caused by malaria. But others claimed that before she lost consciousness the child said she had been beaten again.

For Geraldine, the news was a terrible surprise.

She said: "It would be easy to feel despair but that doesn't do any good. All we can do is feel glad that we helped make her life a little happier before she died."

It is almost two years since Geraldine first visited the Ugandan village of Kabbubu. In that time she has learnt the hard way that she must stick to the battles she can fight and leave the things she can do nothing about.

It has been a rocky journey for a woman who, at 51, was looking forward to a sedate and enjoyable retirement when she first flew to Africa in 1999.

She said: "If anyone had told me Geoff and I would end up doing something like this, I wouldn't have believed them. We're just Mr and Mrs Average."

Geraldine went to Uganda as part of a trip organised by friends she had met at church. At the time she wished she was going somewhere like the Seychelles. Africa had never appealed and she was worried Uganda could be dangerous.

But when she got to Kabbubu, Geraldine met a vicar who told her a story that would change her life forever.

Pastor George Walakira told her white people had come to the village in 1930 and built a medical centre, which transformed the health of the villagers.

But by 1935 the foreigners had left and the centre fell into ruin. The villagers' health worsened and when the Aids epidemic struck, hundreds died.

George remembered his grandmother predicting that one day white people would return to help the people of Kabubbu. But she died without seeing her prediction come true.

Hearing the story, Geraldine was seized with a desire to help the people rebuild their disease-ravaged community. The feeling was stronger than anything she had ever known.

She said: "Even as George's grandmother lay dying, she had hung on to that belief. Yet there had never been any sign of people returning to help. Something about that haunted me. It was like a spell that had to be broken."

It was the unanswered hope of the story that made Geraldine feel so unbearably sad.

In a time when almost every family in the village cares for a child whose parents have died from Aids, hope is the most valuable commodity of all.

And it was the power of this hope, however fragile or tenuous its hold, that compelled Geraldine to disrupt her comfortable, middle-class life and dedicate herself to the orphans of Kabbubu.

In February 2000, Geraldine returned to the village with her husband and two friends. She had asked to meet 12 orphans so she could find out what she could most do to help them. Instead, 400 showed up.

"It was such an overwhelming feeling - all of these children looking at us for help, barefoot and dressed in rags. I felt like I just wanted to escape and go home, because it was too much for us to deal with. But I knew it was already too late for that.

"When we started talking to the children and asking them about their lives, they all had these big ambitions to be pilots or doctors or nurses. I thought they would have had no hope left but instead they inspired me to have hope too.

"They had held on to their dreams and it was those dreams that kept them going."

Life can be harsh for everyone in a village such as Kabbubu, where poverty is widespread. People live in mud huts, often sleeping on the floor, and there is no sanitation system.

But for the orphans, the future is even more bleak. Often cared for by relatives who cannot afford to keep them, many are made to feel unwelcome or unloved. Yet they still manage to hang on to their dreams.

When Geraldine and Geoff asked them what they needed most, they all agreed on a school.

Education was even more important to them than healthcare.

"They really relish the chance to learn, because it makes a difference to their whole family. They can finally feel useful and wanted, because a child with an education could become the family's breadwinner."

When the couple returned to their home in Cowbeech, near Hailsham, they set up a charity called the Quicken Trust. The name comes from an ancient word meaning 'to bring back to life'.

Their first goal was to build a school. But the village elders also gave them a long list of other things they needed, including a borehole for fresh water, a medical centre and accommodation for the teachers.

Instead of appealing directly for money, the couple would give talks at schools and churches. They sold handcrafts made by Kabbubu women and asked their audience to spread the word.

By September last year, Geraldine and Geoff had raised £40,000 to build a primary school for all 400 orphans.

In the following months, they persuaded a Ugandan charity, Ambassadors of Hope, to build the school.

They found staff with the help of headteachers from neighbouring villages and they set about finding sponsors back in England to help pay for the children's education.

Now, the school and its pupils are thriving. The couple's latest project is to rebuild the medical centre that first sparked Geraldine's interest.

After that, they hope to set up farming projects and a football pitch. Together, they are creating a newly invigorated community.

There are days when Geraldine wishes she had never gone to Uganda.

Instead of pottering in her garden and enjoying spending time with her three grandchildren, she jets off to Kabbubu three times a year to sleep in a mud hut and eat mashed plantain and maize porridge.

She said: "We live in a lovely house in a nice part of the country and sometimes it is a wrench.

"It's hot and sticky out there, very dusty and physically uncomfortable. Sometimes I really have to gear myself up to go.

"Geoff was hoping to retire at 55 but we have spent a lot of our own money on getting out to Uganda even though BA pays for our flights. He will have to work for a bit longer now.

"It has taken over our lives in many ways. I haven't seen my grandchildren since March and when they do come and stay I will have to clear a space for them in the spare room.

"At the moment it is full of things our sponsors want me to take to the children.

"But then I remember that we are really making a difference and that's when I realise it is worth the sacrifice.

"My son is grown up and doesn't live at home any longer.

"I love being a grandmother but in a way this is like being a mother again. The children call me momma, which is really touching. I never thought I would end up being a mum to 400 orphans."