The headlines are calling it a Holocaust musical, a phrase so loaded with bad taste that it immediately conjures images of Springtime For Hitler, the show in Mel Brooks' The Producers created to guarantee Broadway failure.

But headlines can be misleading. Imagine This, which began previewing at the New London Theatre this week, is a musical. And true, its story, which takes place in the Warsaw Ghetto in 1942, is, of course, set against the background of the Holocaust.

But responding to the headlines after the musical was announced in July, American TV producer Beth Trachtenberg flatly rejected that her first stage production was a Shoah show.

"It is not about the Holocaust. It's about a group of people... who manage to hold on to their humanity, to find a way to laugh with each other and love each other and exist," she said.

Five months on and after production costs have reached between £4.5 and £5 million, the Jewish writing team, consisting of the bearded and bear-like Israeli composer Shuki Levy and his American collaborators Glenn Berenbeim (book) and David Goldsmith (lyrics), are taking a break from rehearsals.

Imagine This represents a first for each of them. For Levy and Berenbeim it is their first musical. Levy - a self-taught musician and son of a barber - is best-known as a recording artist and the composer for children's television shows such as Inspector Gadget. Berenbeim "worked in the mines of television", chiefly on the American evangelical show Touched By An Angel. He sounds glad to have moved on. And although Goldsmith has several shows to his name as a lyricist, none made it to New York and this is his West End debut.

All three are being led to the quietest room in the theatre, a route which takes them through dingy backstage corridors via the venue's shabby green room where members of the cast are hanging out after rehearsing one of the show's more emotional scenes. It is the one where a group of Jews end their Passover meal by deciding to kill themselves. And the setting is not Warsaw but Masada. And the persecutors are not German, but Roman.

This is the clever plot twist to Imagine This. The show's heroes and heroines belong to a Jewish theatre company. Led by Daniel Warshowsky (Peter Polycarpou, who was in the original cast of Les Miserables), they attempt to raise the morale of their community by staging a musical about the Jews of Masada who resisted the Romans.

"When I heard that the subject was Masada, my heart just sank," says Berenbeim. "The notion of Jews killing themselves on top of a mountain, with Romans as the enemy. And this was just after Russell Crowe had won the academy award for playing a gladiator?"

"I wanted to tell the story of Masada but from a different angle," says the laid-back Levy, whose sonorous Israeli drawl is tinged with a Los Angeles twang. "I wanted to tell it as the whole message of freedom, rather than look at it as a mass suicide story. That was my goal."
"But Shuki's music swept over me," continues Berenbeim. "It reminded me of when I was a boy and I'd seen Lawrence of Arabia and how the music swept over the sand towards you. Shuki's music had that kind of romantic pull. I was thinking of the subject matter and how to tell this story and I don't know where it came from but it was one of those flashes that writers talk about - and I never get. It occurred to me that the curtain could open and you are in the Warsaw Ghetto in 1942 and there is a Jewish acting company putting on their version of the story of Masada."
Berenbeim's flash of inspiration also excited lyricist Goldsmith. "I immediately saw this group of Jews on a mountain surrounded by Romans, and this group of Jews in a ghetto surrounded by Nazis - and that is too brilliant to pass up."
Levy may be right. Pairing the 2000-year-old story of Masada with that of the Warsaw Ghetto 60 years ago could be an inspired piece of storytelling. There are even comparisons to be made between the Romans and the Germans. "After all, Hitler chose his seig heil salute from the way Roman emperors were saluted," points out Berenbeim.
But this show is nevertheless being viewed by many West Enders as one of the riskiest major productions to arrive in London for some time. Recession is not the best time to open a show. Despite Trachtenburg's assurances, some Jewish theatregoers may balk at a musical that has even the slightest connection with the Holocaust.
No doubt with this in mind, the producer launched a charm offensive. Journalists were invited to rehearsals so that they could see that this show is being done, if not in the best possible taste - that is for the critics and audience to decide - certainly with the best possible intentions.
One of the two Jewish members of the ensemble, Roy Litvin, spoke movingly about his grandmother, a Holocaust survivor. And Trachtenberg even organised a "Sabbath dinner" for the mainly non-Jewish cast "to get everyone in the right frame of mind". Okay, it was on a Monday, but it is the thought that counts.
But even if Jewish theatregoers are reassured, will gentile theatregoers think that a story about Jews in a ghetto is primarily for a Jewish audience? Apart from Litvin, the writers, Trachtenberg and one other member of the ensemble, it is being pointed out that everyone else involved in the production is not Jewish, including director Timothy Sheader, who is also the artistic director of Regent's Park's Open Air Theatre.
This, of course, will not be the first musical to feature Nazis. From The Sound of Music, to the aforementioned The Producers, with Cabaret in between, they all prove that if you get the tone right there is almost nothing you cannot portray onstage. But there still remains a view held by many that to musicalise a serious story is to trivialise it. Is this a worry?

"I think that the problem we have initially is that people are reacting to what they think is the subject - and what we're asking them to do is react to our treatment of it," says Berenbeim. "I don't think anyone would have been interested in the mid '60s if you had said you were doing a musical about pogroms in Russia. And yet when you see the story that emerged out of Anatevka..."

"I'm aware how it's perceived," says Goldsmith. "It's not how I perceive it, which is how the show can reach people's hearts and minds. It is never my intention to trivialise any subject I would take on."

For Berenbeim, Imagine This can also serve as a history lesson. "And if you understand the depth of the meaning of ‘Never Forget', I find it paradoxical that when a subject comes up that is this important and this powerful, and whose very existence is being denied by antisemites, isn't this the right time to say to the world, this is a story that is part of never forgetting?"

"I believe that some things are meant to be," says Levy, ever the laid-back one of the trio. "I don't think anyone will be offended. I think people will come out and be inspired by it. It doesn't worry me at all."

Imagine This opens on November 20 at the New London Theatre, London WC2. Information and tickets on 0844 412 4654