There is as much reason to celebrate the UK premiere of the musical Rothschild & Sons as there is to regret that it was ever written. The show, which started previews at the Park Theatre this week, was inspired by Frederick Morton’s bestselling 1961 book about the banking dynasty. But the biggest selling point of the show is that it is written by Jerry Bock and Sheldon Harnick. Who wouldn’t look forward to a new (to UK audiences) musical by the writers of Fiddler on the Roof?

But The Rothschilds, as the original 1970 show was called, ended the Bock/Harnik writing relationship. It was directed then by the British director Derek Goldby, perhaps best known for the first full scale production of Tom Stoppard’s breakthrough play Rosencrantz and Guildenstern Are Dead at the National Theatre. According to Harnick, Goldby was the wrong choice for that first production.

“Jerry became extremely friendly with him [Goldby] and I did not,” Harnick tells me, from his New York home. “I felt that we had hired the wrong man. He was capable, but not for our show. And it caused great problems between Jerry and me. At the end of that show, Jerry went off in his direction and I went mine.

“We remained friends [because] we had too much business in common that we had to take care of. But we didn’t write together any more. Also, Jerry was a very capable lyricist and he wanted to write his own songs. So that was something he pursued”

Was the separation a source of regret for Harnick?

“It was source of great regret. It still is” says the 93-year-old. However, he is not sure if Bock, who died in 2010, felt the same way. “That’s a good question,” he says with a wry chuckle. “I’d like to think he felt that way but I don’t really know.”

Directed by Jeffrey B Moss the London production of Rothschild & Sons is a rewritten version of the original show which received its New York premiere while the original production of Bock and Harnick’s Fiddler on the Roof was still playing nearby on Broadway. Moss’s later production, also first seen in New York in 2015, cuts the show down to one uninterrupted 100-minute act. Sherman Yellen’s book follows the fortunes — and the fortune — of Mayer Rothschild (played by Robert Cuccioli who led the 2015 production) and his five sons, from the family’s modest beginnings in the Jewish ghetto of 18th-century Frankfurt to 19th-century London.

Given the current reputation of bankers, is this a story that Harnick would have chosen to write today?

“I would very much want to write about it now,” says the lyricist. “Our show is not about banking so much as a family that was hemmed into a ghetto with very little prospect of improvement. It’s about how they managed to not only get out of the ghetto out but make a life for themselves. They became very rich. But getting rich is unimportant compared to how they managed to improve themselves.”

Still, it is possibly a good thing that Rothschild is not the Harnick/Bock character who gets to sing Fiddler’s If I Were a Rich Man, which might not sit well in a story about a man who actually became one of the richest men in the world. Even if Rothschild did get to sing it, his motive would be very different from Tevye’s. For Rothschild, money was a way to escape the ghetto. For Tevye, money meant physical comfort, and maybe a little status, too. As Tevye (actually Harnick) puts it, he’d have a house with:

“One long staircase just going up,

And one even longer coming down,

And one more leading nowhere, just for show.”

Another crucial difference between the real-life Rothschild and the fictional Tevye (created by Sholem Aleichem) is that whereas Tevye tries and fails to prevent change, Rothschild tries and succeeds in bringing it about.

“I think that’s a good way to look at it,” says Harnick. “Their situations were so different. Tevye coming from a more or less rural community and Rothschild coming from the city. So they had different problems.”

Another difference is that Tevye has always been embraced by every country and culture where Fiddler on the Roof has been performed. But the name of Rothschild has become a lightning rod for antisemitic international conspiracy theories.

They “come and go” says a sanguine Harnick, though he accepts that recently they have more often come than gone. Still, his shows have helped to fight the libels.

“One of the things Jerry and I were happy about is that Rothschild & Sons, like Fiddler on the Roof, presented Jewish people as human beings with all the faults of other human beings so that people could identify with them and not make devils of them.”

Yet this was never the motive for creating these shows, says Harnick who will be present at Monday’s official opening of Rothschild & Sons.

“No,” he says. “We loved the stories and did our best to realise them on stage in terms of book, music and dance”.

‘Rothschild & Sons’ is at the Park Theatre, Finsbury Park, until February 17.

www.parktheatre.co.uk