By Katie Engelhart, special to CNN

LONDON (CNN) - The Sunday Assembly was riding high.

The world’s most voguish - though not its only - atheist church opened last year in London, to global attention and abundant acclaim.

So popular was the premise, so bright the promise, that soon the Sunday Assembly was ready to franchise, branching out into cities such as New York, Dublin and Melbourne.

“It’s a way to scale goodness,” declared Sanderson Jones, a standup comic and co-founder of The Sunday Assembly, which calls itself a “godless congregation.”

But nearly as quickly as the Assembly spread, it split, with New York City emerging as organized atheism’s Avignon.

In October, three former members of Sunday Assembly NYC announced the formation of a breakaway group called Godless Revival.

“The Sunday Assembly,” wrote Godless Revival founder Lee Moore in a scathing blog post, “has a problem with atheism.”

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