Some years ago, a small theatre in Sweden had the chutzpah to mount their own version of the Dreamworks animated film The Prince of Egypt, based on the Exodus story.

They had not sought permission from the film company, or the writers of the script or the songs. Their ambition was considerable, especially considering the epic nature of the film, which includes, of course, the parting of the Red Sea, the Ten Plagues, the Burning Bush and a memorable chariot race. Not the easiest film to translate to the stage.

No doubt they assumed that their location meant they were far from Hollywood’s notice. Little did they know that one night in the audience sat the film’s book writer Philip LaZebnik and songwriter Stephen Schwartz.

“We were in Copenhagen, and we learned of the Swedish version,” Schwartz recalled this week. “So we drove over and saw it. Of course it had been thrown together. But it confirmed that it was stage-worthy.”

Fast forward 15 years, and The Prince of Egypt, the musical, is about to have its world premiere in London’s West End at the Dominion Theatre. Previews start tonight, and the official opening is at the end of the month.

Schwartz was back in America for a flying visit when I spoke to him, but this Sunday he's at JW3 in conversation with West End stars Caroline Sheen and Michael D. Xavier. So what took so long? Why was it such a long wait for the musical? 

“Musical theatre takes time,” says Schwartz. In fact, ever since the film came out in 1998 there had been talk of making a stage version, a plan given a boost by seeing that Swedish version. But plans stalled when Dreamworks was bought out by Universal. Fortunately the new bosses agreed to go ahead and, for five years, Schwartz and LaZebnik have been working on the new version, a normal gestation period for a musical, says Schwartz, even one where story and songs already exist.

The Prince of Egypt was the first project for Dreamworks, the company set up by film director and producer Steven Spielberg, former Disney executive Jeffrey Katzenberg, and music executive David Geffen. They wanted to make an animated version of the Exodus story that would outdo Cecil B DeMille’s 1956 classic epic movie The Ten Commandments. The Dreamworks version broadly stuck to the biblical version of events, with its focus on the young Moses growing up as a member of the Egyptian royal family alongside the pharaoh-to-be Rameses. When Moses learns that he comes from a family of Hebrew slaves, he knows he will have to take on his childhood friend to free his people. The film was met with acclaim, and Schwartz won an Oscar for the song When You Believe, which was recorded by Whitney Houston and Mariah Carey and became a global hit.

For the stage version, Schwartz tells me, “we had to consider how to tell this story for a very different media. There are only six songs in the film so a great many more were needed. More songs, reworking existing songs, finales, reprises…We also had to work out how to theatricalise elements of the film, for example the chariot race. It’s been a lot of work, but a very exciting process.”

Five of the original songs have made it to the stage, including, of course When You Believe. Its Oscar wasn’t Schwartz’s only win. He’d won two Oscars for Pocahontas, and netted six Tony nominations for his stage work, from Godspell in 1972 to the smash hit Wicked, which has been seen by 60 million people worldwide. The London production, at the at the Apollo Victoria Theatre is now the ninth longest running musical in West End history. It was the London producers of Wicked who saw a developmental version of Prince of Egypt and decided to put it on here, no doubt hoping for the same box office success.

Schwarz, now 71, grew up in a “very secular” Jewish family in New York, so secular that he did not have a barmitzvah, although now he celebrates Jewish holidays with his family. “Jewish holidays and the others. Passover and Easter. Chanucah and Christmas. Both new years.”

His parents were avid theatre-goers, and early on in life he realised that musical theatre “spoke to me”. This cultural background, he suggests may explain why so many American Jews took a similar path. “Every Jewish home had a piano,” he says. “There was a time when pretty much every musical theatre composer and lyricist was Jewish. Now, not so much.”

He had a classical training in piano and composition at the Juilliard School of Music while in high school and studied drama at Carnegie Mellon University, graduating in 1968. Within a few years, he had three productions playing on Broadway including his first big hit, Godspell, a distinctly Christian-themed show, based around hymns and the Gospel of Matthew.

Around the same time, he worked with Leonard Bernstein on the English text and lyrics for Mass, Bernstein’s reworking of the Catholic Latin mass. Commissioned by Jacqueline Kennedy, it was inspired in part by Bernstein conducting at Robert F Kennedy’s funeral.

But, over the years, Schwartz has taken on some Jewish themes. Rags the Musical, set in the New York garment trade was a flop when it came out in 1986, but after rewrites was revived, most recently at London’s Park Theatre, where it was praised by the JC’s theatre critic John Nathan as something which “can even be spoken of as a companion piece to Fiddler on the Roof”.

And then there is The Prince of Egypt. Musically, Schwartz says it is “very much based in both Jewish and Middle Eastern music — Jewish and Arabic. There’s a different musical scale and different instruments. From a musical point of view it was good to explore.”

He doesn’t see musicals as belonging to any one religion. The Prince of Egypt tells a “universal” story, he says, about people who are caught up in events larger than themselves. Obviously, Jewish people think of Passover, there’s a special affinity. But the appeal is not limited to those people.”

That given, I suggest to him that his biggest hit Wicked, had a very Jewish feel to it. It’s a backstory spin on The Wizard of Oz, based on the novel Wicked: The Life and Times of the Wicked Witch of the West by Gregory Maguire. Telling the story of the green-skinned witch Elphaba, and her blonde, preppy friend Gilda, it’s a powerful tale of prejudice, which Maguire says was inspired by demagogues, including Hitler. Schwartz and book-writer Winnie Holzman’s show invites audiences to think about power and its misuse; who is really good and who is wicked.

“I think a lot of musical theatre themes speak to Jewish audiences,” says Schwartz, “because in many instances musicals are about outsiders, striving to discover how they might fit in.

“That’s the story of Hamilton, Billy Elliott and Wicked — none of them so- called Jewish musicals.

“Wicked is not overtly Jewish-themed but it certainly resonates with many Jewish people’s experience.”

He’s experienced success and failure in his career, and scoffs at the notion that there is such a thing as a formula for a hit. “Find a story you want to tell that will feel fresh and theatrically exciting,” he offers, adding that most successful musicals offer a “message of hope.”

In America, there’s little of the snobbishness that sometimes can blight the format in the UK. This is partly because of the Jewish musicians like Bernstein and George Gershwin who moved between genres. “Musical theatre is so ingrained in American culture,” Schwartz says. “Now is a good time for musicals.” There’s a lot of interest —he cites the film La La Land — musicals are being rediscovered, and new talent celebrated.

So what’s his advice for new writers? “Write! Work hard and then try to get people to hear what you are doing. That’s what a lot of young people starting out are doing. Some are very young, writing at university.” He’s thinking of Toby Marlow and Lucy Moss, writers of the hit British musical Six, about the wives of Henry VIII written in their final months at Cambridge, which opens on Broadway next month.

“Talent comes out,” says Schwartz. And, with The Prince of Egypt on stage, 22 years after the film version, he proves that once out it doesn’t go away.

Stephen Schwartz is speaking at JW3 on Sunday February 9

The Prince of Egypt is at the Dominion Theatre, in preview until February 25