A TALL man in red trousers with a beard worthy of Robinson Crusoe is trying to generate what he calls "whizziness" from the front. As the band provides some suitably animated accompaniment, he asks the packed congregation to join him in a cheer, and, game at 11 o'clock on a wintry Sunday morning in north London, they respond readily.

For a churchgoer, it is all oddly familiar. We are sitting on small, hard wooden chairs, in an "arts and performance space", the Nave, which shares what was once St Paul's, Hackney, with a Steiner school. There are welcomers at the gate, tea in the foyer, and a projector at the front.

"There are still a few seats left, and there's always upstairs!" a slightly flustered vicar-type cries. The gathering has all the appearance of a church likely to be branded "vibrant" by the diocese, and held up as a model for attracting young urbanites. The congregation is largely under 35, and looks as if it might have spent the previous evening at a synth night in Shoreditch.

But this is not church, in the strictest sense of the word. It is the first meeting of the Sunday Assembly, listed in Time Out (under "Comedy") as a place where a "congregation of Godless people meet to celebrate the wonders of life". Devised by the comedians Sanderson Jones (of the red trousers) and Pippa Evans, it is open to "anyone who wants to live better, help often and wonder more".

In a spirit of wonder, we kick off with a song: "What a wonderful world" by Louis Armstrong. Tip one from years of churchgoing: get the projector screen higher ("I know very little about picking font sizes!" quips the ever-likeable Mr Jones, as people struggle to recall exactly what Satchmo said about roses). Now, for an inspirational reading: "The Man in the Arena" by Theodore Roosevelt ("his place shall never be with those cold and timid souls who neither know victory nor defeat").

Today's theme is beginnings. "Starting things is so hard," states the promotional material ("latecomers go straight to HELL!"). "There's the dread of work, the bogeyman of failures past, and future, and all manner of mental booby traps that prevent you from getting going."

It is a great topic, and tackling it is a guest speaker, Andy Staton, a children's author who wrote his first book after "almost a decade of dropping out and dead-end jobs". He is self-effacing, rambling, and seems a bit embarrassed about having a point. Perhaps that comes with the territory: it's hard to know what is expected of anyone in week one. But, against a backdrop of stand-up comedy and irreverence, there is perhaps a pressure to be flippant and to shy away from suggesting that you, in any way, hold any answers.

Time for the second song: "Don't look back in anger" by Oasis, with a cracking oboe solo.

Next up is Ms Evans, who is not only leading on guitar and vocals, but talking about her recent trip to Moscow. It's a funny, clever reflection on a city where people aren't "nice", and where the police Taser you if you fall asleep on the Metro.

Finally, it falls to Mr Jones to wrap things up. If he was a clergyman, this is the part where he would ram home his three points, possibly all starting with the same letter. He gets his laughs. The cries of preachers in the United States have an echo of the police patrolling a Hackney estate, he says: "Can I get a witness?"

The Christmas story is told in the Church of Scotland (where he grew up) with all the joy of breaking the news of a tumour, he suggests. He is confessional, too. He realised recently that the megaphone voice in his head reminding him of past failures was, in fact, that of his father, who days earlier had accused him of leaving today's address "to the last minute, as usual".

Today, he wants to encourage people to believe in the possibility of achieving their goals. We are asked to close our eyes and visualise achieving something, and then how we might feel at that moment. A sneaky peek suggests that perhaps earlier speakers needn't have worried so much about embarrassing people with sincerity: all eyes are dutifully shut.

But it is a matter of seconds before it is all brought to an abrupt close ("I don't know how long these things are supposed to go on for!") and back to gags, whizziness, and some enthusiastic cheering.

If the collection is anything to go by (we throw money into an empty projector box, plates being in short supply) the godless congregation gets what they came for. It will more than cover the £200 venue hire and cost of tea. Mr Jones seems genuinely surprised and delighted to have a packed venue, and it is his exuberance that carries the day.

Still, it is an odd blend of stand-up comedy and motivational speak, and low on wonder (although, to be fair, that's next month's topic). To hear that "There's nothing before and nothing after," may sound thrilling to a fairly content 30-year-old living off Upper Street, but perhaps less so if you're in crisis.

Call me biased, but the theory that "If you believe it, really, anything is possible!" is arguably much easier to disprove than the existence of God. Still, the jokes are excellent, and red trousers are almost mandatory in South Ken. Someone get this man on Alpha . . .