In 1984, a small group of teenagers travelled to a remote part of East Africa to help construct a village water project which their school had funded. From this modest beginning has sprung one of the most enduring links any British school has built with the developing world.
This summer, 15 years after that first trip, students from Cranbrook School in Kent were again in Africa, the sixth time a group has gone to live and work alongside villagers in the Tabora region of Tanzania.
Many schools now enjoy contact with less developed parts of the world. Some organise school-to-school exchanges, while others send students trekking in exotic locations, but the steady, committed support of aid projects in a single region of central Tanzania by Cranbrook School - a 13-plus, co-educational state day and boarding school on the Kent-Sussex border - is of a different order altogether.
The extended contact has allowed strong bonds to develop. It has brought practical help to a region which badly needs it and, just as importantly, allowed real friendships to flourish and greatly enhanced the school's own culture, community and curriculum.
"I don't know of any other school that even comes near to doing what we do," says Rod Smith, head of sixth form, who set up the link and continues to mastermind it. "I don't think you could be a student or a teacher here and not be aware of Tanzania.
"I remember one boy who put himself forward to go on one of our trips when he got to the sixth form because he said he always remembered the first assembly he heard on Tanzania, just after he joined the school."
More than 70 students have spent time in Tanzania and about pound;80,000 worth of aid (in today's money), has been donated. With just one glance around the staff-room Rod Smith can identify at least three other teachers who have spent a summer in Africa - trips which both students and staff describe as life-changing.
"It's really hard, both physically and mentally," says Emma Loxton, a former drama and music teacher at the school, who helped lead a group two years ago. "There's a different diet, a whole new culture. There's no light and no running water and your food can be a goat, led in on a string. I remember some of the girls saying, 'Miss, we can't eat that!' and me saying, 'Well you're going to have to!' "But it was also a fantastic experience, and there were so many times we laughed and laughed and laughed."
The Tabora region of Tanzania, just south of the equator, grows crops such as maize, groundnuts and cassava, and rears cattle and goats, but facilities can be sparse. Some villages are so remote that Cranbrook school students were the first white visitors.
Over the years the school has provided wells and piped water, bought a Land-Rover, built primary school latrines, refurbished college and health clinic facilities, built college housing and painted classrooms. It has hosted visits from Tanzanian college principals and teachers and donated money, much of it from the students' own annual fund-raising efforts.
"The students always get to vote on where they want their money to go. This year they voted unanimously for pound;7,000 to go to Tanzania. They like the idea that they can see exactly where their money is going," says Rod Smith.
Pupils interested in the school's Africa connection can join a weekly community service group which packs books, writes newsletters and keeps in touch with the school's link partners - two rural development colleges in Tanzania. Fund-raising includes "Tanzanian" discos, refreshment stands and Christmas cards, while art classes have used Tanzanian artefacts for still life drawing, and instruments in music lessons.
Visiting Tanzanian teachers have contributed to classroom discussions on development issues such as poverty, contraception and the role of women, and to talk with students about the relationship between Christians and Moslem communities back home.
There have been other curriculum spin-offs. Sixth-form biologists, historians and geographers have used their time in Tanzania to compile project papers on various aspects of African life, while younger science students, back in Kent, have got to grips with tasks such as building a fuel-efficient stove and designing ways to ventilate pit latrines.
Inevitably, in a school of 700, not everyone is equally enthusiastic about the link. Fund raising can clash with the needs of other cash-hungry school projects. One Year nine student confessed that when fund-raising for a forthcoming Africa trip is at its height, "you can sometimes feel as if you'll scream if you hear another word about Tanzania".
Yet in a school that won praise from OFSTED two years ago for its "unique" commitment to fund- raising for charity, which "focuses pupils on those less fortunate than themselves and helps them understand the life and culture of other countries", the value of this long-running project is widely recognised. Both parents and teachers support the small Devon-based charity, the Friends of Urambo and Mwanhala, through which the link was first set up and with which the school has worked ever since.
At the Tanzanian end, many people put time and effort into maintaining the link, especially the principals of the Folk Development Colleges in Urambo and Mwanhala, and Elias Masatu of the regional administration, who says that not only does the partnership bring practical aid to the region, but also offers "a way of meeting people of different nationalities, cultures and races, and being able to sit down with them in a friendly way and exchange ideas".
The link has now spread even wider. A number of school leavers have returned to the region for their gap year, and others have begun careers in aid and development.
The scheme has even produced its first Anglo-Tanzanian family. Joe Pullen, who first went to Tanzania as a sixth former, then returned for his gap year, now has a Tanzanian wife, Euni, and a three-year-old daughter, Chantelle.
"Many people out there work as subsistence farmers, and won't see pound;10 from one year to the next," he says, "but to me the quality of life is every bit as good as in England, if not better."
It was when I was standing on my ceremonial stool, in my ceremonial robe, with my bow and arrows, being made an honorary commander of the Sungu-Sungu of Mbooga that I realised how different this school trip was from any other.
After we landed in Dar-es-Salaam the 12 of us (six boys and six girls, aged between 16 and 19) our three leaders, and some local helpers travelled for five days in a small, open lorry to our first destination.
Since this lorry was also crammed with equipment and clothes for the villages we were going to stay in, there was hardly room to move. We all had to learn that we were going to have to become more patient and tolerant, as well as understand that in Africa three hours' travel could easily mean 30!
Our first long stay was in Mbooga, an extremely remote village, with no electricity, no roads of any sort, no one who spoke English, and where there had only ever been the occasional white visitor. Our group was a big focus of interest, and we were made very welcome.
Every morning we broke rocks and mixed concrete to help build a new health clinic - the nearest hospital was two days' walk away.
We had thought we would have to live under harsh conditions, but we actually lived very comfortably in a barn with hot water for washing and perfectly edible food - rice (lots of rice!), goat, spinach, tomatoes and beef, although we'd had to help skin our own cow!
My name was pulled out of a hat to represent the group as a commander of the Sungu-Sungu - the local village police force - and the highest honour the village could give us.
The next village was Kaliua, where we helped build a kindergarten. We soon turned into skilful bricklayers and by the time we left all the walls were up to roof level.
Tanzania is the second poorest country in the world, and sometimes we did see malnourished and poorly-clothed children. But at the same time, although people had few possessions, they seemed very happy.
Everyday life didn't seem like the hard view of the Third World we are often given, and in many ways families and communities seemed much more supportive of each other than we are in the West.
However we all sometimes found the trip hard, some of us got ill, and we were often taken aback by how slowly things got done, and the "we'll-cross-that-bridge-when-we-come-to-it" attitude. Still the culture shock on coming back home was, for some reason, far greater than going.
David Dickson, a pupil at Cranbrook School, spent five weeks in Tabora this summer.