Elder Karges and Elder Bång are men on a mission. Can they get someone interested in the Church of Jesus Christ of Latter-day Saints before they reach the Tesco car park? Kade Karges, 20, from Arizona, and Marc Bång, a 21-year-old Dane, discuss their gameplan as they unload copies of the Book of Mormon from their car's packed boot. The gold lettering on the dark-blue covers is in several languages. "We normally take a Hindi one with us. We find it comes in useful," Bång says. There is a quick prayer and the young men, sporting dark suits and name badges, are off.
The pair may seem incongruous on the sunny streets of Feltham, West London, but they are among 750 such missionaries stationed in the UK and 50,000 throughout the world. The majority of these elders and sisters are between 18 and 25 years old, engaging in a two-year stint away from home that for many is like a religious gap year.
Bång originally hoped for an assignment in a Spanish-speaking country, but when he opened the envelope it was London. "I just felt a really good feeling," he says. His own parents converted to Mormonism before he was born when missionaries knocked on their door in Denmark. "I've always felt a desire to do what brought me happiness," he says.
Karges nods vigorously. He andBång are like a married couple. They live, work and pray together, even cooking communally on their slow cooker. On the road, they take turns to drive their mission car, analyse Bible passages and explain exactly who they are to passers-by. The average shopper is polite but bemused. "This morning,"Karges says, "someone asked us if we were Jehovah's Witnesses." Most Brits tend to associate Mormonism with one word, polygamy, although it was outlawed bythe Church of Jesus Christ in 1890. We may be hazy about a definition for it, but today Mormonism is one of the fastest-growing faiths in the world. There are now 13.8 million members worldwide, 185,000 in the UK, more than the number of Buddhists registered by the 2001 Census. This is a huge rise from its beginnings in New York in 1830, when Joseph Smith published the Book of Mormon - a chronicle of the sacred history of an ancient American people as delivered to him by an angel.
The US sociologist Rodney Stark has compared the rise of Mormonism with that of Christianity in the Roman Empire. And in his new book, Shall the Religious Inherit the Earth?, the author Eric Kaufmann notes that "throughout their history, Mormon fertility has tracked the total American fertility at a rate of one to two children above the national average".
Its growth overseas is also impressive. "It's partly religious supply fanning out of the US towards the developing world," Kaufmann says. Countries that previously followed folk religions have particularly high rates of conversion (more than 20 per cent of Tonga now are practising Mormons) but the Church's real power base remains the US, in which they have just become a larger group than Jews. "They are no longer fringe," Kaufmann says. "They are very committed, wealthy and educated. And they've had a presidential candidate."
Most American mormons live in Utah - 60 per cent of the state's population belong to the Church. The temple in the city of St George is the oldest still in use. Glaring white, it stands incongruously among the clapboard community. Near by, the local supermarket stocks everything except alcohol. Two teenagers stop to pass the time in the frozen foods aisle. Do they know that there is a Mormon missionary school in the UK? "Oh sure. It's really famous."
The overcast hills of Lancashire are a long way from Utah's canyons but they are just as important in the Church's history. Mormons venerate this area as the oldest continuous branch of their faith. Joseph Smith first sent missionaries to Preston in 1837. They preached in Herefordshire marketplaces and baptised converts in the River Ribble. Today, Chorley houses one of only two missionary training centres (MTC) in Europe as well as an imposing temple, which opened in 1998. More than 10,000 missionaries trained in the UK have served around the world. President Clegg, the MTC's American head, personifies this transatlantic connection. His great-great-grandfather was one of the first people baptised as a Mormon in this area. Clegg has served in the UK three times: first as a missionary, then as head of the Manchester branch; and now overseeing new students at the MTC.
"They keep sending me back here insisting that maybe this time I'll get it right," he says jokingly. The temple spire, topped by a golden figure of the angel Moroni, is a local landmark. The 15-acre site around it falls somewhere between a business school and a military barracks. Not a blade of grass is out of place: only the wandering ducks are unregimented. A shop sells white temple outfits, books on interfaith relations and a "Be Super" postcard, which shows a missionary suit bursting out from under a Superman shirt. Identical beige buildings host visitors, genealogists and, of course, the missionaries. The rooms inside the MTC seem to fit the usual college model. That is until you hear the strains of harmonised singing of Come to Zion echoing along the hallway and see the sign over a box of free Polos that reads: "Missionaries don't chew gum - so have a mint!"
The clean-scrubbed, eager faces that gather for three weeks' training are the descendants of Smith's early acolytes. There are 26 of them from eight different countries. Dressed conservatively in dark suits or long skirts, they are mostly aged about 21. Some are from four generations of church families. Others, such as Nikke Karjalainen, from Finland, are used to being the odd one out. He was the only Mormon in his school. "It's not a new thing in a way to tell about the Church to someone who hasn't heard," he says .
Many of them are taking time out from degrees or full-time careers. Nicole Müller, 21, from Switzerland, hopes that the skills gleaned from her day job will help her on the streets. "I was a hairdresser so I have a lot of practise talking to people." She has brought her scissors with her in case she can keep her hand in on her classmates.
For the moment, Müller is taking notes in a class conducted with the enthusiasm of a motivational lecture.The timetable pinned to the wall is crammed with companion inventories (designed to stop you from fighting with your partner and apparently helpful later in married life); group meetings (with tips on how to cope in the field: hostile people reject the Church, not you); and Scripture classes (possible lessons are drawn from the Old Testament as well as the Book of Mormon). Every so often, a DVD featuring senior church leaders plays for inspiration.
Down the hall, an online chat session with outsiders who come to the Church's website exposes missionaries to the curious - and to the cranks - in cyberspace. "I think he's jerking us around," says an elder about a correspondent. Converting the unsaved is a 24-hour business in the technological age. When these young men clock off, their peers in Utah take over.
In another room, students giggle as they try to find a Bible verse, but they are a dedicated crew. Many would-be missionaries start saving the pennies as children to cover the £10,000 cost. During their mission, they call home twice a year and e-mail once a week. They are up early and in bed early, eschewing the traditional student crutches of alcohol and caffeine, which are forbidden by their Church. They practise sport regularly, many with their badges still pinned to their T-shirts.
Cedric Habicht, a 24-year-old from Germany, admits that he hopes to see a Premier League football game during his busy UK schedule. He arrived in Chorley straight from active service in Afghanistan for the German Army. "I struck a deal with God," he says. "When I come back in one piece from Afghanistan, I want to go on a mission. If that happens, I'll know that's what He wanted me to do."
The students move to their missions next week. The majority are going to Birmingham, but some will come under the care of President Lyle Shamo and his wife Tracey, who head the England London South Mission. In 1965, Lyle did his service outside Bristol. Now retired, he recollects nights spent in a room above a Barnstaple stable. "It was so cold and the smell so intense, I thought I was going to die."
Nonetheless, when he found out that the Church wanted him to return to the UK, he was delighted. "It's a dream come true. I feel like I've come home."
There have been enormous changes while he was away. The infrastructure of the Church in the UK has grown hugely and within Europe the senior church leaders are now all European. Tracy says: "There are now more members outside the US than inside."
As he describes the Church's belief that the family unit endures eternally, Lyle begins to weep with emotion. He and his wife already have eight children and sixteen grandchildren but are now responsible for all the young missionaries in their area. "I'm the mom," Tracy says proudly. They hadthe missionaries shovelling snow-filled driveways last week. "We don't want them to become Bible bashers or stand in people's way in the street," Lyle says. "We tell them to always be respectful."
Mormonism places Jesus Christ in the centre of its beliefs. But the Church's independent brand of Christianity is not always recognisable to other denominations. "For a Christian, the gospels stand and Jesus is the final and ultimate revelation. We don't add other books as they have," says the Rev John Goddard, Bishop of Burnley, "But I would want to emphasise the quality of some of their people."
Steven Hughes, the interfaith development officer for Churches Together in Lancashire, says that Mormons "are the one group who rarely cross my radar". He lives just eight miles from the Temple Complex, but rarely sees the missionaries out and about.
Karges and Bång have been up since dawn and still have hours packed with meetings and lessons ahead. As they walk the streets, they politely tell an interested teenager that he'll have to check with his parents first, smile at a woman who takes a rather more aggressive approach and strike up a conversation with another who'd like to know more.
This last woman is a Russian-speaking Latvian. The elders jump to try out their language skills. They have only two phrases. "My name is Elder Bång" and "I know the Book of Mormon is true". It seems to be enough. Out come their appointment books and in goes their next attempt to save a soul.