Plans to set up almost 400 “atheist churches” on five continents are underway after the extraordinary success of one small congregation that began holding godless services just over a year ago.

Word about the religion-free church spread like wildfire after the first Sunday Assembly was held in a deconsecrated church in Highbury, North London, in January 2013. By September, 100 congregations will be holding services from Singapore and South Africa to Sao Paulo and San Diego. A further 274 teams currently are working on plans to launch their own assemblies.

The church’s first General Assembly is being held this weekend with leaders from all over the world gathered in South London. In 150 years of the Anglican Church’s Lambeth Conference, it’s safe to say none has begun quite like this--with a raucous group karaoke rendition of “I’m So Excited,” but then Sunday Assembly is a very different kind of world religion. Their gatherings resemble traditional church services with singing, lessons and the chance to interact with members of the community. The only thing missing is God.

Sanderson Jones, the group’s leader and CEO, and a stand-up comedian by trade, says the young organization is replicating the traditional church structure as it expands. But he says the empire is also attempting to harness the organizational knowhow and social interaction of Grindr and the National Rifle Association.

“This is the first time we’re coming together like this,” he said. “We’ve had such a short time but I think we’re going to build something magnificent, something that’s going to last.”

The group’s rapid expansion has caught everyone by surprise. It is currently growing by 26 per cent each month but there is no end to Jones’ ambitions. “There are 1.1 billion non-religious people in the world,” he told The Daily Beast. “We want to have a godless congregation in every town, city and village that wants one.” In other words, as he told the gathering of leaders on the opening day of the conference: “We’re going to need a bigger boat.”

In order to help as many people set up assemblies as possible, Jones has started to study the mechanics of running a huge organization. “My Twitter feed has got a lot less funny -- people are wondering ‘why is he retweeting a pdf of different corporate governance structures in social enterprises?’” he said. The research has led him to marvel at the N.R.A., one of the few organizations with what is considered the holy trinity of benefits and service, a membership community and a media platform. “Another good example is Grindr and Tinder,” says Jones. “If St Paul was alive today he wouldn’t be writing letters he’d be writing code.”

Jones is constantly exploring ways to create an equally efficient network with even bigger growth potential, but this weekend before he got down to all that, it was time to get down. The lyrics of the second track of Saturday’s musical opening, Pharrell Williams’ “Happy,” were projected on a big screen.

Clap along if you feel, Like that’s what you wanna do.

They did. Two women from The Netherlands swayed from side-to-side; an enthusiastic chap from Newcastle, in the northeast of England, danced in front of his seat in the auditorium; and a broad-shouldered man with graying dreadlocks from Tennessee clapped in time with the music.

That man was Landry Butler, 46, a designer from Nashville, who became co-organizer of his local Sunday Assembly back in November. He was raised in a deeply Christian family, who often took him to three different church services every weekend. “I gave it up for Lent,” he said with a deep laugh. “We’re right on the buckle of the Bible Belt. More than 90 percent of people in Nashville are Christian and not everyone approves of what we’re doing. A lot of people tell me I’m going to Hell.”

“My mother didn’t want to talk about it until I appeared in the newspaper, and then she got interested,” said Butler. “She still says she’s praying for me, but that’s okay. We’re not trying to sell atheism - it’s not for me to get involved, no matter what stupid crap people believe.”

While Butler is setting up an atheist bulkhead in a deeply religious area, Jan Willem van der Straten is operating in a totally different environment. The 24-year-old is working to open the first Sunday Assembly in Amsterdam in September. He was brought up in a secular family, and his parents were stunned when he started taking an interest in religion. He still describes himself as a Christian. “People used to say: ‘Ah, Willem, you can have a good beer with him, but he’s got this funny religion thing.’ For the first time this is a church that my friends might want to come to,” he said. “I don’t have the baggage of religion; I have the baggage of atheism.”

As the assemblies multiply and spread, the disparity between communities has thrown up a series of issues. One of the hot debates to be decided this weekend is whether to continue to use the word “godless.” For those in countries where religion has receded in recent generations it feels more natural to say Sunday Assembly is a "celebration of life." The American chapters argue that everyone would assume it was a religious group if you didn’t explicitly explain otherwise.

The continued prominence of Christian belief in the U.S. also affects the way atheism is seen. The church suffered its first schism earlier this year when New York organizers fell out with the founders over the strength of the anti-religious teaching. “They wanted to do a celebration of atheism not a celebration of life,” said van der Straten, who has been working at the London headquarters for the past three months.

The genius of Sunday Assembly is that it shares far more with an ordinary church service than it differs. There have been scores of atheist groups in the past, but few have attracted such warmth and affection.

“The thing that we’ve got is that we’re the only non-religious service that works. Rationality is part of it, but we also have the emotional connection,” Jones said. “We are speaking to the whole human.”

Sunday Assembly is already talking to an awful lot of humans. Jones wonders if they might manage to start 2015 congregations by 2015. “It might just be a little bit historical if it goes on like this. We could have a profound impact,” he said. “Throughout history there’s been these moments when an idea takes off: the Great Awakenings. We could suddenly create a great moment.”