When the retiring and hugely popular Very Rev John D Miller finally vacates his council house in Castlemilk after his last church service tomorrow, ready to begin a new mission in Africa, at least 200 hopefuls will be waiting to hear if they are to be its next tenant. "Such is the demand for social housing," smiles the handsome 65-year-old wryly, neatly ignoring my joke about the vagaries of clerical celebrity. Rather than feel guilty that he's kept the house out of the reach of the area's most needy for the past 21 years, he prefers to believe he's actually preserved it for them.

His rented family home, a classic 1960s design with a small front and back garden, is popular with locals because it is one of the very few original council homes in the area that has not gone into private ownership. Thus the next family to live there will be doubly blessed.

Such a gesture is typical of the Oxford and Edinburgh University graduate who, when first posted to Castlemilk East Parish Church in 1971, controversially chose not to live in the detached Victorian church manse in nearby leafy Rutherglen, because he preferred to live among his people.

"It seemed ridiculous to live in a manse with a large billiards room when my whole parish was in corporation housing," he explains.

His conviction was strong enough for him to face the wrath of the church's disciplinary committee - which, he says, "had no choice but to go along with it, but concluded that my decision was unwise'". The manse has since been sold, but another will be found for the incoming minister.

Oxford-born Miller's move was all the more apposite given that he is a true "son of the manse" who spent a part of his childhood in a big Kilmarnock manse, when his father was minister, before moving to care for three parishes in Crieff. His grandfather was minister of the United Free Church in Borgue, Galloway, and his great-grandfather was minister of Ruchhill parish church. His own church is a modest 1958 affair, the windows of which are protected with mesh glass, and it is clearly a focal point of local activity.

Miller expects the new tenant of his Castlemilk home - which he, his wife Mary and their three children were allocated after 15 years in a council tenement flat - eventually to buy it. But he is heartened by recent amendments to the right-to-buy legislation ushered in by the 1980 Thatcher government - the social effects of which stick in Miller's famously dog-collarless craw.

He is pleased that the 2005 amendment to the law means tenants must now wait five years rather than two before applying to buy a council home, and must wait five years rather than three before selling. If they sell within the first 10 years, the property must first be offered back to the council.

The continuing need for social housing in his area is an issue close to Miller's heart. Over the 36 years of his ministry in Castlemilk, broken only by 12 months in Edinburgh as Moderator of the General Assembly of the Church of Scotland, Miller has witnessed "huge, enormous, cataclysmic social upheaval". The decline of heavy industry and the consequential loss of blue-collar employment has seen a dramatic population decline of two-thirds from 49,000 to 14,000. Traditional tenements have been demolished, to be replaced by terraced houses, which to Miller translates as "eight families down to two in the same space". He notes the "positive imagery" put on new mixed housing stock, but frets for the worst-off people who "struggle on" unnoticed. He reckons the brutality of that social change and its effect on local people has never been officially observed.

"The biggest single change in Castlemilk has been the disappearance of its population," he says, "and the social housing decisions of the past few years have led to greater social division than ever before."

He blames party politics. "It was about the Tories wishing to break up the Labour dominance of housing. They ended the rate support grant to local authorities so there was nowhere in council budgets for the maintenance of housing. This meant that when a family left, the house was left empty and vulnerable to theft and decay. Closes were evacuated, then whole buildings were pulled down, then whole streets disappeared. When that happened, the threads of community life went. You don't see that happening in suburban areas."

The consequential menace of drugs is growing, and he feels the fact of their criminality has created a "hermetically sealed parallel culture" in the housing schemes that is untouchable by government policy. "From the outside you wouldn't know anything was going on, but from the inside there are people making money, keeping others in place with violence and fear." Yet he has managed to maintain a parish of 200, approximately the same size as when the population was three times greater. Typically, Miller ascribes this not to himself but to the innate spirituality of his flock.

"I look to other ministers in other parishes and realise I've never had to argue for the existence of God," he says. "The people here haven't dismissed that dimension to their lives. They are always dealing with the big issues of life and death, good and evil, violence and peace, yet still want to be associated with the positive views of faith. They're still glad of having it and still want to express that in the church situation.

"I see a daily recognition of the spiritual element to life out there on the pavements of Castlemilk."

For all his politically potent words, Miller is the epitome of deference. Such is his lack of ego that it's maddeningly difficult to get him to talk about himself. He peppers his conversation with phrases such as "I'm sure this can't possibly be of interest to you", and says he doesn't know how to use his mobile phone. When we finally meet, as arranged, he is standing in the middle of his tiny kitchen counselling a needy parishioner and has an urgent meeting to attend in 15 minutes. We go to his church and find a room to talk, but he's tense. He only relaxes when showing me around his parish.

His long-time ally, Fr Willy Slaven, parish priest of St Simon's Roman Catholic Church in Partick, explains his friend's apparent evasiveness. "John's availability to others is what defines him. He's got his ego much better managed than the rest of us."

Even so, such political awareness seems unusual for a man of the cloth. His daughter, Sarah, is the newly appointed head of research for the Scottish Labour Party. "How can I answer that question?" he replies, bewildered, when I ask if he's politically motivated. "It seems to me that everything is political. In our society, the church tends to have a conservative role, but I understand my role is to have a solidarity with people who are in the struggle of the human condition."

Another of these continuing struggles is religious divide. Miller has written about how it remains rife in all sectors of life in the west of Scotland, and how in his locality, "infants learn young, dressed in their pram in the colours of a favourite football team". He refuses to vocalise what awfulness he has witnessed, but as recently as last year he wrote: "I have seen the havoc wrought when conflict fuelled by religious division has brought violent death."

As he departs, does he feel sectarianism is at last losing its sting? "I think it's not going to go away," he says quietly. "With the building of two new secondary schools and four primaries in Castlemilk, we had the opportunity to initiate a shared campus, but the idea was rejected by the local authority, so we have two separate secondary schools." He was not invited to be part of the decision-making process and sees this as "a missed opportunity".

Yet Miller is recognised as having crossed the religious divide, so much so that one of the new non-denominational primary schools is to be named after him, while its neighbour is named St John Paul II. Is he saying that separate schools engenders sectarianism? "I think sectarianism is illustrated in separate schools, not caused by them."

He feels this is a worrying precedent for our fragile multicultural society. "State funding of faith schools gives an excuse for funding being extended to other faiths in the future. It will be difficult to deny the same to other faiths, and I'm anxious about that situation."

In September, he and Mary - who have been together 40 years - move to Zimbabwe to work with HIV/Aids victims in a mission hospital. He is reluctant to talk about his new position, and is characteristically modest about it, saying only: "What we are doing is a very insignificant thing."

He will certainly not forget the people he leaves behind. "It's extraordinary to be in the same place for so long, and I can't imagine being in a better place than Castlemilk," he says. "Yes, the quality of life in the schemes is difficult, but it is also so rich. There's endless tears and endless laughter. I feel privileged to have been part of this community. The sorrow for me is that it has to come to an end at all."

If his flock has remained faithful against all odds, has he himself ever felt swamped by hopelessness?

"I've often had a sense of being driven more by despair than by hope," he admits. "But if pushed I'd always pin my life on hope."

A friend and colleague who enriched many lives

RON FERGUSON John Miller is one of the nicest, brightest, most modest, least pretentious and most able people in the church. I've known him since the 1970s, when I was community minister in Easterhouse and he was in Castlemilk.

I know from experience the kind of things he and his family have been exposed to - the smashing of windows and the burglaries - but also the unforgettable privilege of learning new life-lessons from quite fantastic people.

We were part of a group of ministers and priests working in inner-city Glasgow or out in the big housing schemes. What we all had in common was the radicalising experience of living and working in situations which challenged all our familiar assumptions about the church.

I cannot think of anyone I know who has less awareness of himself as a heroic individual than John. Yet his understated manner is deceptive: this was the man who, on July 4, 1975, ceremonially burned his dog collar, after a night of wrestling with his conscience. He came to the conclusion that it was more a barrier than an asset - although he knew this would upset some traditionalists. His own Independence Day was significant, yet this man who describes himself as "a traditional parish minister" is no trendy cleric.

One of the first decisions he and his wife, Mary, made when they went to Castlemilk was to persuade a reluctant Presbytery of Glasgow to allow them to move from their comfortable manse in Rutherglen into a council house in Castlemilk.

He believed that if he were to be a minister to his people, he needed to share their living circumstances: the lack of amenities, the poor facilities, the boarded-up houses, the outbreaks of gang warfare. This was a costly, but immensely enriching, decision.

But what I most want to say today is that my friend John Miller could not have achieved what he has without his partnership with Mary, who has also made a hugely significant contribution to life in Castlemilk. If John is the reluctant hero, Mary is the equally diffident heroine. Typically, they will be embarrassed by what I have just written, but on this special occasion they will just have to grin and thole it.