When my mother first became interested in joining the Mennonites, I knew practically nothing about them. The little I did know came from my cousins. Their parents had recently converted and they were finding it difficult to accept. My aunt and uncle had travelled all over the world and were living in Brazil when they found a community of Mennonites near the tiny town of Rio Verde. Taken with their lifestyle and attitude, they decided to move from their small farm near Cuiabá to join the church. My mother visited from the UK, and returned enraptured by the experience. The Mennonites, she said, were unlike any other people she had come across, and she, too, was thinking seriously about joining.

The Mennonite church traces its origins back to the 16th century European Anabaptist movement - a group so named because of its rejection of infant baptism. They are named after Menno Simons, a Swiss minister who was one of its most prominent members. At its foundation is a literalist reading of the Bible and a rejection of all outward signs of faith that are not a reflection of an inner state of belief.

There is a strict dress code. Men and women must not dress alike: men must grow their beard and women must not draw attention to themselves by wearing makeup or jewellery. Women wear simple, homemade dresses and a traditional head-covering that symbolises their place in a biblical order that has God at the top, then man, then woman. They are also barred from activities considered unnecessary, wasteful or corrupting - among these are watching TV, going to the cinema or theatre, drinking alcohol, playing musical instruments, dancing and taking photographs. All of this they do in an effort to, as a Mennonite tract states, "live a life of cross-bearing, self-denial, unselfishness, and submission".

I had no idea how painful I would find my mother's conversion. One day, I came home from London to Birmingham and found my picture turned to the wall. It was a self-portrait I'd painted for Mum during my university days. I was broke and it was all I had to give. "I can't draw fingers," I'd said, and she laughed, but she loved it because I'd made it myself. In the years since I'd left home, Mum had moved quite a bit, but the painting always went with her, taking pride of place.

But her new beliefs meant she had to get rid of all pictures of people, me included. Only the painting remained on display. She had turned it to the wall to get used to it not being there.

On another occasion, she handed me a box filled with her jewellery. In it were gifts from me, including a silver ring I'd bought her for her birthday. Seeing Mum wear things I had given her made me feel like we belonged to each other. Getting them back, I felt rejected and utterly bewildered.

"Either I give up on the church altogether, or I make these changes," she said, struggling with her crisis of faith. She's the only parent I have. My dad left before I was born. I decided to try harder to be supportive, but couldn't shake the feeling that, once the pictures were gone, I might be next.

In common with many children of single parents, I felt I was responsible for my mother's wellbeing. As a child, I contracted Guillain-Barré syndrome, a rare illness that attacks the nervous system and leaves one paralysed.

I spent 18 months in hospital. I was acutely aware of the toll that months of daily visits to hospital had on Mum. I resolved then, aged five, to protect her. I would be as good as I could be so that she would never again have to suffer because of me.

Yet my life in London consisted mostly of the things that she was no longer allowed to do. I was working in theatre and taking advantage of the social wonders of the city. I was also struggling with my own crisis of faith.

My mother had been raised in a staunchly Christian, Jamaican home. She abandoned the church in her teens, but by the time I was 12 - mainly at my instigation - we were evangelicals, going to church together. There was praying in tongues, healing of the sick and conventions held by American evangelists. It was a circus of confusing messages, which left me feeling anxious, permanently guilty and depressed. Leaving was an act of self-preservation. I didn't tell my mother. I was worried I would upset her.

As I gradually lost my faith, hers was gathering strength. She started making her own clothes - a simple, shift dress according to a pattern that had been sanctioned by the Mennonite church. She no longer dyed her hair, something she had been doing for so long I was shocked by how grey she was. She looked older, and that upset me. There are only 20 years between us, and I'd always been proud of my young mum.

Then she rang to tell me that the Mennonites had given her some money so that I could visit our relatives in Brazil. The trip had two functions: to find out more about the Mennonites for myself and to go to my cousin James's wedding. He had converted, along with his parents, and had met someone he wanted to marry. Her name was Claudia. I had heard stories about their courtship: they were never to be alone together until the night of the wedding; they met only at regular meetings for unmarried youths or at family gatherings; my cousin's proposal was delivered via the elders of the church. I was both horrified and intrigued.

There were 368 baptised members of the Mennonite church living in Brazil when I visited. I know this because I have consulted their yearbook for 2006, which catalogues every Mennonite church worldwide. It lists not only the addresses of churches in each country, but also the names and addresses of its leaders. This leadership group includes the head of the sewing circle (Mennonites are famous for their quilt-making). The English community had a population of seven: my mother, my aunt and uncle, and four of their children. In Latvia there is only one member.

The community I visited was made up of about 50 houses and two churches, scattered over a vast stretch of farmland. It has its own school, a hydroelectric generator (built by members of the community) and a publishing house. They produce and distribute everything from tracts to cookery books. It is a place where your closest neighbour may be a drive away, but you definitely know their name.

I was struck by their generosity. Not only had they paid for my ticket to Brazil, they also provided my aunt and uncle with a house and car, free of charge. Mennonites live the doctrine of giving sacrificially. If they have two coats and you have none, you will soon find your wardrobe bursting. They are not allowed to have insurance - if you need medical care, someone in the community will stump up the cash.

Without the distractions of career or entertainment, their lives revolve around each other. Dining tables go on for miles - there are usually 24 settings, and we were invited to dinner practically every meal. And being there, I understood how, after years of being an isolated, single parent, Mum was now immersed in family life. It is a life where, despite the insistence on a particular family order, men spend as much time at home with their wives and children as they do out working. I knew that I couldn't feel the same way. They were lovely people, but I found their insularity stifling and unenlightened. I longed to come home. Mum was her own person and could do whatever she wished, and so must I.

I returned to my own life. I sought counselling to help me to deal with my mother's conversion and what it might mean for our relationship.

Then, in a move that might seem strange, I went back to live with my mother. Mum had always said that her door was open should I need to return, so, with mounting debts, it seemed the most obvious solution. I was apprehensive. I still hadn't been explicit about my loss of faith and was worried about telling her and of what would happen if I didn't. As is my way in difficult situations, I tried to be funny. I told her that if I came home, I wasn't joining the Little House on the Prairie sweatshop. She thought it was hilarious.

Apart from the clothes, she hasn't changed that much. I write for the stage and it is still painful that she can't see any of my plays, but we make an effort with things we can share. We eat together, play board games and chat. And it does seem to have made her happier. She's certainly easier to live with. When I left home in 1997, my mother was obsessive about tidiness. She couldn't get to sleep if the ironing board was still up. Her Bible studies have led her to believe that it was her pride that made her nag. She is now much more tolerant of crumbs and dishes in the sink.

Before writing this piece, I asked her how she felt about the article, about me. She shrugged and said: "The article doesn't bother me. All you're going to do is tell the truth." She told me that she doesn't judge me, that she loves me and that she always thought I was "an interesting person".

"My only responsibility," she said, "is to love you."

The Mennonites she'd spoken to had agreed. She also asked me to say that it's not a new religion "It's still the old one. I'm just doing it properly this time."

Despite our religious differences, I think our relationship is much stronger now. In fact, without being forced to confront our differences, I might not have had the courage to be myself. I feel now that I can be honest with Mum and that, even when she doesn't like what I say, she will still listen. I try to extend the same privilege to her.

I think tolerance is the word for it.