Ten years ago David Baddiel took part in the genealogy documentary show Who Do You Think You Are?. His grandfather Ernst, a German Jew, had fled his native land with his family, weeks before the Nazis invaded Poland. 

For comedian and presenter David, born 19 years after World War Two ended, the programme was a chance to delve deeper into his past. For his mother Sarah, it was an opportunity to make a huge revelation. 

“It was something my mum had never told me before, but decided to say on camera,“ says David.

“Essentially she thought her parents weren’t her real parents. That my great-uncle Oti, who died in the Holocaust was her real father and that she had been given to Ernst, Oti’s brother, because his family were able to get out of Germany.

“I still don’t know if that’s true or not. Even after all the work on the programme, the problem we have is that he was killed and there’s no record of his death. But there are a couple of weird things – like my mum has two birth certificates. But this was war time Germany, there are lots of possibilities as to why that might be.“

Identity is clearly a theme which preys upon David’s mind. There’s been a book: The Secret Purposes, based loosely on the story of his maternal grandparents. 

And then there’s the film The Infidel, which has been transformed into a musical, set to be staged at Theatre Stratford East next week.

“You know, I’ve never really thought about it before,“ says David, 50, pausing. “But the idea for The Infidel –  a comedy which revolves around a British Muslim, who goes through an identity crisis when he discovers he was adopted as a child and born to a Jewish family – must have been linked to what my mother said. It must have been on my mind. 

“I find that sense of confusion about your ethnicity intriguing. 

“There’s also the fact that when I was putting together the story, I was looking at Omid (Djalili, who plays the lead role in the film), and I had this idea that he could be Jewish or he could be Muslim. 

“A joke I used to do in my stand up, was about two blokes wanting to beat me up, one because he thought I was a Jew, the other because he said I was a paki. I couldn’t correct either of them, because either way, it wasn’t going to help.“

Some might argue that David’s had remarkable foresight to be staging a musical, which sends up religious differences between Muslims and Jews, given current conflicts.

“Some might say it’s trouble,“ David laughs. When the film came out in 2010 it felt pretty on the knuckle of the news then.

“The Infidel is not trying to be blasphemous, the faiths involved are treated with reverence. But religious people should be sent up. The ideas that Muslims have about Jews and Jews about Muslims are played about within The Infidel. Plus, I’ve found with the musical, if you do something controversial, but you do it in song, you can more or less get away with it.

“The message at the end of the day is that it’s the same God. Despite all the war and trouble, it’s the same God.“

David’s never been one to shy away from using his comedy to cause controversy. The middle child of three brothers, he grew up in Dollis Hill, Willesden, attending the North West London Jewish Day School in Brent, before moving onto Haberdasher’s Aske’s Boys’ School in Elstree.

It was at the latter he realised he had a talent for the comedic, learning that no subject was off-limits: “I decided to do lots of sketches about teachers I hated in the sixth form school review. I don’t know if I’ve ever gone down as well. They wanted to expel me, but because I was going to Cambridge, they didn’t, because it would look bad for their league tables. They have me among their notable alumni now, along with Sacha Baron Cohen and Matt Lucas. 

“But that was my first comedy, I could hear this incredible laughter and I thought, this is it, I’m going make comedy my career.” And he has. 

After graduating from university with a double first in English, there was sketch-writing for radio, television appearances, the writing partnership with comic impressionist Rob Newman, and the subsequent pairing of the two with Hugh Dennis and Steve Punt for The Mary Whitehouse Experience.

Perhaps what he’s most famous for is his work with Frank Skinner and the subsequent blokey reputation the pair cultivated, with their sofa-sitting, beer-swilling commentary on Fantasy Football League, No 1 footie anthem Three Lions and the Baddiel and Skinner Unplanned. 

He has an aversion to fame – “it’s an absurd thing to me, I get confused with Ben Elton, who I’m not, by the way,” and he’s insistent notoriety hasn’t changed him: “Fame doesn’t change you, kids do, I’m still the same bloke from Brent.”

Despite his mainstream popularity, among critics, he’s had something of a tough time – he’s been referred to as ‘The not-so-funny one in Newman and Baddiel; the Ernie Wise of alternative comedy’, so you’d forgive him for feeling nervous about how The Infidel, the musical, will be received. 

“Nervous... curious... interested to see how it’ll translate...,” the father-of-two muses.

“British critics were very sniffy about the Book of Mormon when it came out, I remember someone saying that they wouldn’t criticise Muslims or Jews... well we’re halfway there with this musical.

“I mean, there’s songs called Sexy Burka and Put a Fatwa On It. I’m hoping people will see the musical as a positive experience. Who knows, they may come out singing the songs... perhaps against their better judgement.”

The Infidel is at Stratford East, Gerry Raffles Square, Stratford, E15 1BN, from October 4 until November 2. Details: stratfordeast.com, 020 8534 0310