LONDON, UK — Earlier this month, hundreds of Londoners bundled in wool hats and coats descended on an auditorium off a quiet, tree-lined square in the posh neighborhood of Bloomsbury to celebrate the third Sunday of Advent.

However, inside there was nary a bible, hymnal or cross in sight.

Onstage, Sanderson Jones — who’s been described as a hipster messiah for his ginger-bearded likeness to depictions of Jesus — was decked out in a silver tinsel scarf, Santa hat and customary oversized spectacles.

“So here it is Merry Christmas, everybody’s having fun,” he sang, gyrating across the stage in an upbeat rendition of the English rock band Slade’s “Merry Christmas Everybody.”

With him was Pippa Evans, a fellow comedian. The two are co-founders of a godless congregation called the Sunday Assembly.

Later, a choir of 30-somethings wearing holiday sweaters chimed in with a version of the Pogues’ “Fairytale of New York” as a grey-haired man accompanied them on the fiddle.

At least 300 people attended the Sunday Assembly’s first holiday service, trading carols for Christmas-themed pop songs, a magician in lieu of a priest and a secular lecture on feasting instead of a sermon. Only one Christian trapping remained unchanged: the collection.

“This is a celebration of the values of Christmas, but without the religiosity,” Evans said, her blond hair tussled in disarray.

Jones and Evans describe their unconventional services as drawing on all “the best bits of church” but without the religion.

That appears to fill a need. According to a recent study, 17 percent of atheists occasionally attend religious services around the world.

Tim Lawler, 52, who attended the service with his 9-year-old son, said he was attracted by the sense of community.

“I had this as a child, a community based around a parish church, but the mythical aspects of that left me long ago,” he said. “The Sunday Assembly has a freshness and honesty to it. It’s about opening your mind to a sense of wonder.”

Nearly a year since its first meeting in a deconsecrated north London chapel, the Sunday Assembly (motto: live better, help often, wonder more) is also beginning to charm nonbelievers across the globe: satellite assemblies are cropping up across Britain, Australia and the United States.

The movement’s founders recently returned from a “missionary tour” in America, where they set up branches from Washington D.C. to San Francisco. They want to build a movement that can expand globally, with the hope of hitting 1,000 assemblies worldwide within a decade.

The comedians have even launched a crowdfunding campaign on Indiegogo with the ambitious goal of raising $800,000 to make the dream become reality.

Although the drive fell far short, Jones says he didn’t expect his movement to become as popular as it has. “We thought that it would expand,” he said, “but not at turbo-charged viral Internet success rates.”

The assembly’s popularity underscores a shifting tide in religious identification among Britons. Nearly half say they don’t belong to any religion, up from 31 percent in 1983, according to a 2008 survey by British Social Attitudes.

More people also say they don’t believe in God. Only one in five born since 1975 is a believer, the survey says.

David Voas of the University of Essex in Colchester says that self-identifying as “not having a religion” is becoming increasingly socially acceptable and may trigger further declines in religiosity.

“There’s even an argument in Western Europe that we’ve reached a tipping point where it is less socially acceptable to define yourself as religious than as non-religious,” he says.

Back at the Sunday Assembly, Jones says he doesn’t define himself by his non-belief.

“In the same way that I don’t believe in unicorns or leprechauns, I don’t believe in God,” he said.

Very few people at the service identified themselves as anything at all.

“I don’t believe in anything except people,” said Katy Vans, 39, a member of the choir. “We want everyone to feel that they’re welcome here, that’s what we think we’re doing differently from other organizations.”

Although the Sunday Assembly may seem novel, the desire for a non-religious church-like experience isn’t new.

Nick Spencer, research director at Theos, a Christian think-tank, points to a British movement called the ethical union a century ago.

“It was a resort for people who had that famous Victorian crisis of faith and couldn’t bring themselves to believe anymore,” he said, “but desperately missed everything that belief gave them: purpose, identity, community, direction, hope.”

Conway Hall, where the Sunday Assembly gathered this month, is a relic of that period.

The imposing brick building is home to the Conway Hall Ethical Society, started at the end of the 18th century to advocate secular humanism. The atheist scientist Richard Dawkins is among those who’ve spoken there.

Unlike him, however, the Sunday Assembly doesn’t share a fervent antitheism.

Sanderson and Evans want to distance their movement from the “atheist church” label promoted by the media. That’s prompted the New York chapter to splinter from the assembly and form its own more defined atheist organization called the Godless Revival.

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That didn’t put a damper on the fun in Conway Hall.

Katie Brinsmead-Stockhold, 29, who’s been a regular at the Sunday Assembly since summer, dragged two friends out of bed to join her for the service.

“It’s really the happiest thing you can do on a Sunday,” she said.

The bleary-eyed bunch — dressed in Christmas tree, snowman and Santa sweaters — chatted in animated tones and danced during the holiday pop-song sing-a-longs.

After the service, Jones invited the entire congregation to join him for drinks at a local pub.