Ampleforth Abbey and College, home to 100 Benedictine monks and school to more than 500 boys, spreads in a vast campus across a south-facing slope of the North Yorkshire Moors - to all appearances an unassailable male bastion of the Catholic Church.

But here, as in other spheres of the Church, old traditions are breaking down. The school’s recent announcement that it will go fully co-educational in the sixth form from 2001, is significant, but only one more step for a monastic community meeting the challenges of a rapidly changing world.

When the Benedictine community of St Laurence, first driven out of Westminster by Henry VIII, then driven out of France by the Revolution, settled in Ampleforth at the beginning of the 19th century, it opened a school run entirely by its handful of monks, one purpose being to increase the number of vocations.

It was highly successful and until the 1960s the community continued to expand. With 150 monks it was the largest Benedictine monastery in western Europe - a powerhouse of Catholicism in England that provided the last English Cardinal, the late Basil Hume. A fallow period was to follow, with vocations falling away, but unlike many monastic communities, which suffer from ageing populations, Ampleforth has a healthy number of younger monks. Few of these were boys at the school however; they come from all walks of life - one was a doctor, another a health service administrator - used to working with women professionally.

Increasing numbers of women, hundreds every year, now go on retreat to Ampleforth. Monks who work in the monastery’s mission parishes in Lancashire and Merseyside are chaplains to voluntary-aided schools, most of which have become co-educational. There has been a significant increase in the number of female teachers at the school where lay staff, many having taught previously in co-educational schools, are now in the majority.

For the past five years, therefore, there has been a great deal of informal discussion about bringing girls into the school, not least because there is no Catholic girls’ boarding provision “between Edinburgh and Ascot”, apart from Stoneyhurst, a Jesuit school in north-west England. Moreover, Father Leo Chamberlain, Ampleforth’s headteacher, has received growing numbers of requests from parents of daughters hoping that the school would open its doors to them.

Cynics could point to the declining popularity of boarding education, particularly for schools in more remote areas, and therefore deduce that there are also strong financial arguments for taking in girls; that this step has come out of economic necessity rather than any real belief in the benefits of mixing the sexes.

Father Leo admits to considering long-term boarding trends, but he says the decision has come from a position of strength, not weakness. For the past few years the school has been operating with a “sound surplus”. Last year, Ampleforth increased its pupil numbers by 5 per cent in the teeth of a decline in boarding uptake nationally of 3 per cent. The sixth form entry for September is expected to be the highest ever and the school continues to expand its plant, having completed a pound;3m science and business centre this year. Four million pounds will be invested in new boarding houses for boys in the coming year.

He says: “We have a mission for the Catholic faith and we have decided that this is also about giving girls entry to a Benedictine world - academic excellence combined with a holistic education based on faith and virtue.

“The tradition has been for Catholic girls to be educated by nuns, but most convent schools have closed or now work under lay leadership. Their spirituality tended to be based on the more individualistic Jesuit model.

“Our model is of people trying to live harmoniously and supportively with each other, with all their imperfections, of people striving to stick together, a kind of mutual obedience. That’s a difficult concept for able, thrusting young people to take on board, to sacrifice independence for obedience, but there is something about the community which has attracted old boys back to visit time after time. There is something about it which is unique. They see it as more than just a school and we expect girls can feel the same.”

There has also been a strong belief, particularly among teaching staff, that boys would benefit from schooling with girls, that it would help them to cope better with women socially and professionally in later life, that it would create a more natural environment.

Rachel Fletcher, an English teacher and head of professional development at the school, has been pushing hard for this change. She says: “Boys here miss girls, they miss their sisters and their girlfriends and they are driven into a kind of blokiness. I think things like the first 15 (rugby team) will lose their mystique once girls are here, and that’s a good thing.”

She is confident girls will also benefit from the teaching style. She says:

“Boys tend to be greater risk-takers and we teach to reflect that. We try to make as many connections across the curriculum as we can, to broaden things out as much as possible.” Two years ago Ampleforth announced that it would take day girls on a more formal basis. Six presently attend the school out of 44 day pupils and in September there will be eight, attached to St Aidan’s sixth form house in the centre of the campus. From 2001 St Aidan’s will be the girls’ boarding house, with its own housemistress. Its central position, says, Father Leo, is to show that girls are not just on the fringe, but central to the school.

Anna Borrett, 17, formerly attended a girl’s day school in north-east England, from which she emerged with a string of A-starred GCSEs. But she had brothers at Ampleforth and made a last-minute decision to switch in the sixth form. She studies French, music, Latin and religious education for A-level and plays for the school hockey team. The move, she says, was the best thing that could have happened to her and she welcomes being part of a Catholic religious community. “At my last school I was really quiet. It was like a work factory, we learned what was on the syllabus and little else. Here I’ll have a go at anything; I do a lot of music in my spare time, orchestra, singing, it’s a broad education that builds up strength of character. I also want to prove that I can do what the boys can do.”

Peter Westmacott, 17, who opted to join St Aidan’s in the sixth form from another house, says he has also benefited greatly from co-education. “An all-male society doesn’t reflect a natural balance. It makes sense to have girls. I have changed for the better; I am much more out-going, much more confident. In much the same way that I spent my first nine years in a single-sex house and the change has been good for me, so the change will be good for the school.”

Bill Lofthouse, head of classics and housemaster of St Aidan’s, has previously taught in two other schools, which were also in the throes of becoming mixed. St Aidan’s, he says, is proving how beneficial co-education can be. “I have always believed girls would justify themselves at Ampleforth. There is a very natural, happy environment here, there is much less intensity of rivalry between boys, more sibling-like relationships between boys and girls.”

It is unsurprising that Ampleforth, by dint of its history and tradition and the fact that any major changes in the school have to be sanctioned by the abbot and community, should be one of the last great boys’ public schools to take in girls. But by starting with the sixth form it is treading a well-worn path. Rugby, which took in sixth-form girls in the early Nineties, now has 240 girls in the school alongside 488 boys; King’s Canterbury, which went co-ed about the same time, has 325 girls compared with 428 boys. Ampleforth is expecting a more modest start and has made provision for 25 boarders in the first instance.

There has undoubtedly been opposition. Some parents are concerned that the monastery is breaking with tradition. Some boys are worried that the introduction of girls will break up strong friendships. For a community that is constantly under the media spotlight - men in habits make news - there is some anxiety that it is playing hostage to fortune - that a pregnancy, for example, would break its reputation. Father Leo has nevertheless received letters of support and parental backing in Ampleforth’s unique meetings in parents’ homes.

Sarah Tate, 18, who has spent two years in the school, chose to attend Ampleforth herself, having been home-educated previously. She believes having girls fully integrated into the school will dispel all such prejudices. “Those are the sorts of attitudes that fully-integrated co-education will get rid of,” she says . “For me, co-education means boys and girls stop regarding each other simply as members of the opposite sex and start to treat each other as people.”

Matthew Devlin, 16, an American who has attended the school since he was 10, says: “This business about tradition and what can go wrong if we break it has come up a lot. But why shouldn’t there be changes. It’s good for boys to learn that they can have friendships with girls as much as with boys, that they don’t have to be predatory.”

Father Leo is philosophical about it. “Of course this is the age when boys and girls become sexually aware and in so far as it is a problem it is something we should meet with the ideal, not with a ball and chain,” he says. “We cannot live in suspicion of the worst. Our job is to set up proper parameters for life and to encourage proper relationships. If we set this up in the right way it will be to the good of everybody.”