It's not often member of the audience comes up to you and tells you he loved the play - but you're going to hell.

Well that's exactly what happened to William Gaminara after a performance of The Christians, which has just opened at Notting Hill's Gate Theatre following a celebrated run at the Edinburgh Festival.

The former Silent Witness star plays a progressive pastor in Lucas Hnath's drama, whose attempt to unify the congregation at his mega-church only serves to magnify the divisions among them.

"We had a Jehovah's Witness who came up and said he quite enjoyed the play but thought we were all wrong," said Gaminara. "He said there's a hell and people will go there."

At the other end of the spectrum was the American pastor who said the sermon at the heart of the play, in which Gaminara's character pronounces there is no such thing as a physical hell, was one he wished he'd been able to deliver some 40 years ago.

"He said he wanted to preach that sermon but wasn't allowed to. He had to leave the church as a result, so it certainly resonated with him," said the actor.

There have been no shortage of dog collars among the audiences for The Christians, according to Gaminara, who believes it has proved popular because it casts light on believers' doubts without exposing them to ridicule like so many other plays.

"A lot of people with faith have come to see it and found it really engaging," he said.

"There's often an expectation at the theatre in this country that people with faith are going to be made fun of.

"In this play, everyone's a Christian, but they're all very different Christians and no one's lampooned - you can understand where each of them is coming from."

William Gaminara and Jaye Griffiths in The Christians (photo by Iona Firouzabadi)

"We had a Q&A last night in which one of the actresses revealed she was Christian. She'd never told us that during rehearsals, which I found strange.

"She said she'd been nervous because she felt in this day and age, people pre-judge those with faith."

The Christians is set inside a mega-church, the kind of giant arena rare over here but common in the US, where some pastors are elevated to the status of rock stars.

As part of his research, Gaminara visited the Dominion Theatre in the West End, where services take place every Sunday before a 2,000-strong audience and are accompanied by a live band.

But he believes the play will always be a different beast on this side of the Atlantic compared with the States, where he says 45% of citizens still believe in Adam and Eve.

"It works in a slightly different way over here," he said. "It's about why people go to church, why they have faith and what happens when you start tinkering with that faith.

"I think it's equally relevant to other faiths and also to big organisations generally. If the CEO of a major company suddenly decides to make a change, the repercussions trickle down into the lives of everyone involved in that company."

The Christians is at the Gate Theatre, in Notting Hill, until October 3. For tickets, call the box office on 020 7229 0706 or visit www.gatetheatre.co.uk.

Stefan Adegbola in The Christians, at the Gate Theatre (photo by Simon Dutson)

Review:

When church becomes big business, the bottom line is about more than just saving the congregation's souls.

Pastor Paul has spent the last 20 years building his church from a modest storefront to a cavernous stadium style arena holding thousands of worshippers.

But when the progressive cleric delivers an explosive sermon, shaking the foundations of his congregants' belief, cracks begin to appear.

As members of his flock begin jumping the fence, the church's financial future is threatened. And when even those closest to him start asking difficult questions, he is forced to examine the roots of his creed.

Lucas Hnath's new play, directed by Christopher Haydon, is a fascinating and powerful interrogation of religion, in which faith is no solid bedrock but a writhing mass of doubt, fear and hope.

It raises questions about the ownership of religion and the responsibilities of religious leaders, which are equally pertinent to Christianity, Islam or any other faith.

Delivered in the style of a sermon, with accompanying live music from a 16-strong gospel choir, you feel the full force of the protagonists' convictions.

But despite the subject matter it never feels preachy and whenever you're lured into a moment of judgement there's always a disarming jolt awaiting.

William Gaminara convinces as the inspirational church leader, combining the easy charm of a car salesman with the gravitas of a statesman, and he's complemented by a strong supporting cast.

It's fair to say I'm a convert.