'The old Kylie Minogue theory is creeping in again,' said Charlie Mackesey, standing on a platform in a church in South Kensington, one of the swankiest parts of London. 'We seem to listen to the band passively and enjoy them without getting involved. It requires a lot of effort and screaming to break the ice. So let's get going.'

He started to chant, to the same tune Manchester United followers use to sing the praises of Eric 'Ooh aah' Cantona, the following mantra: 'Jes-us is dyna-mite, Jesus is dynamite. Don't mess with dyna-mite, don't mess with dynamite.'

In front of him 200 or so people immediately joined in. Behind him, a seven-piece rock band complete with two drummers picked up the beat. After a couple of minutes, everyone in the place was leaping up and down like frogs.

'Right,' said Charlie when they had finished. 'Now we're ready to go.'

About once a month, Charlie Mackesey, a 30-year-old artist, leads a service at one of the most unusual churches in Britain: St Paul's, Onslow Square. Here they have a gospel band and choir: not of the traditional type, but one made up almost exclusively of young, white, middle-class people. Can young, white, middle-class people in Kensington sing the gospel? At St Paul's they give it a go.

A session lasts nearly three hours. Last Sunday, for most of that time, as the infectious, rhythmic music pumped out, the congregation were on their feet, dancing, swaying, singing. There were moments of private ecstasy, people fell to their knees, one woman cried, a lot of hands were raised in the air at appropriate moments. But mainly people contented themselves by shuffling around much as they might at a concert by, say, Sting. Oddly, given their enthusiastic behaviour, there was no applause when the songs finished. Instead, Charlie or Nicky Lee, the casually dressed curate, would lead a burst of praying.

'Lord I love you,' said Charlie. 'Anyone else?'

'Spirit I praise you,' someone shouted out.

'Yeah,' said Charlie. 'I like it.'

Fifteen years ago things were rather different at St Paul's. In 1977 the church was closed down, abandoned, a victim of dwindling attendances. The diocese of London had plans for redeveloping the prime-site building.

Just down the road, however, the services at the church of the Holy Trinity, Brompton, were attracting upwards of 900 people. Soon after St Paul's closed down, HTB, as it is known, began sending missionary squads of parishioners to spruce things up in fading churches in its vicinity, a process known as 'planting'. It was thought at HTB that the derelict church in the middle of South Kensington's smartest square could be saved.

'We felt that once you lose a building like St Paul's it will be for ever,' said Nicky Lee. 'Besides HTB was full, and people needed somewhere else to worship. The diocese gave us five years to make St Paul's work.'

Structural repairs required pounds 350,000; the diocese promised half if Holy Trinity raised the other half, a process that proved to be not so difficult in Kensington as it might in less well-heeled parishes. 'We appealed to the congregation at morning service one Sunday,' said Mr Lee. 'And by the end of the evening we had collected pounds 125,000.'

Oh, happy day indeed. The money paid for repairs to the roof, heating, carpeting, the removal of the pews ('we wanted a flexible space'), and a sound system for which most rock bands would give their guitar-plucking fingers. Seventy five people were transplanted from HTB to start things off, including Dave Clifton, a professional musician who has played the guitar for, among others, Tanita Tikaram and Julia Fordham.

'As soon as people find out you can play music, you find yourself roped in,' he said. 'And was I roped in.'

Dave put together a band from the congregation, added some non-church-goers and started to play in services. Such was their ability, people came from miles away to enjoy the band. Within a couple of years, the number of regular attenders had grown to 250. Few, however, came from the expensive, stucco-fronted houses that surround the church.

'We don't have many regulars in the immediate vicinity,' said Nicky Lee. 'Though of course we would welcome them.'

Despite its success, Mr Lee is not convinced that St Paul's could act as a blueprint for other dying churches.

'One of the great advantages we have in central London is that people have a choice. If people want a formal liturgical service, or a charismatic one, they have them to hand, a short distance away. I accept that in a small market town, a church offering our kind of approach might put off as many people as it attracts.'

Nevertheless, as it sees attendances falling all over the place, the Church hierarchy cannot but be delighted with St Paul's.

'The Bishop of London is very supportive,' said Mr Lee. 'His churchmanship may be different but he recognises that we are drawing in a group of people the Church has not been successful in reaching.'

That group is strongly in evidence at Charlie Mackesey's gospel services: middle-class and overwhelmingly under 30. Yet they are not the sort who know the words to Kumbaya; at university, most of them would have avoided offers of coffee from Christian Union members; there is hardly a sandal-wearer among them.

'A lot of friends of mine, not churchgoers, say, 'next time you go to a black gospel service let me come with you',' said Charlie, who wears cowboy boots and his hair in an anarchic tangle of locks. 'They see that as a sociological outing, a piece of anthropology. But when their own peers, nice, white, middle-class folk, behave in a passionate way, they can't handle it. It's too challenging to them.'

Indeed, some of those drawn by the infectiousness of the music seem slightly embarrassed about finding themselves regular churchgoers.

'I went to a convent school and I really got sick of having religion thrust down my throat,' said one woman, a freelance press photographer, who asked not to be named. 'I came here about 10 months ago and now come every week. Sometimes I have to pinch myself because I can't believe after all I've been through that I actually go to church regularly. I know there's a lot of teasing about happy- clappy, but this music really gets me going.'

Charlie Mackesey agrees about the music. 'The first time I prayed in public was the most embarrassing moment in my life,' he said. 'But it is easy to lose yourself in this music. I think that's why gospel services appeal to people you wouldn't expect, like me. In a sense I come here because I just don't feel patronised. I was sick of that aspect of church. At school I went to chapel six times a week. I thought it had put me off the idea for life.'

Unlike many unhappy efforts to modernise church services, at St Paul's no attempt has been made to update existing liturgical structures. There's no banging of tambourines during psalms, or rapping to the Lord's Prayer. Old formats have been abandoned. Sunday evening services are more like a rock concert. At the back of the church, the sound engineer, attending to the mixing desk, wore, in the manner of sound engineers everywhere, a Rush T-shirt and a pair of headphones, hanging unused round his neck.

St Paul's has managed the trick of providing accessibility without sacrificing intellectual rigour. The sermon last Sunday, delivered between bouts of singing, was challenging stuff (mostly about why you shouldn't have sex outside marriage). And, unlike some other charismatic churches, there appears to be a diffident attitude towards evangelising.

'The first thing you think when you start coming regularly is: 'oh my friends will think I've gone barmy',' said the photographer. 'But it's not the kind of subject that comes up often. And I don't raise it. My mum's still a Catholic, I guess she'd think this was completely weird if she knew about it.'

But her mum might have recognised some of it. The service ended, like a good pop show, with an oldie: a stunning a cappella version of the hymn 'When I Survey the Wondrous Cross,' the women in the band providing a flourish of harmonies.

'Yo,' said Charlie, when it had finished to wild applause. 'That's it. We'll try another one of these soon. Er, bye then.'

(Photographs omitted)