Merrily she rolls along with a hit show set for West End

A contented Ms Friedman settles back into her stalls seat, apparently happy with a day of big decisions, some of them about the tiniest details. Just how many steps should Umbers take stage left in a moment of high drama? (“A bit to the left, Franklin,” says Ms Friedman, addressing the actor by his character name. “A bit more. Back a bit. There! Lovely!”)

“I love the staging of it,” she adds, while the cast, still on stage, put in a bit of overtime. “There are moments of clarity when you know that’s the place. Two inches the other way and it’s not right.” On her lap, sits Dot, a pug named after the role she played in another Sondheim musical, Sunday in the Park With George, for which she received one of seven Olivier nominations.

That was her first Sondheim show. The list of notable, often award-winning productions since includes Ragtime, Chicago, Passion and her own show, By Special Arrangement, for which she won her first Olivier. But it was her 1990 appearance in Nicholas Hytner’s National Theatre production of Ghetto, by Israel’s best-known dramatist Joshua Sobol, that launched her on this trajectory. The play with music, set in the Lithuanian town of Vilna (now Vilnius) tells the story of the Vilna Yiddish Theatre group and its extinction by the Nazis. Ms Friedman had not known that her grandparents had come from the town until she was told in a telegram from her father Leonard. He was an eminent violinist who worked all over the world, which is how she came to be born in Switzerland. The telegram read: “Your grandparents love and thank you for keeping their thoughts and words alive.”

This was well before Nicholas Hytner landed the top job in theatre as artistic director at the National and Ms Friedman became known as one the classiest performers in musical theatre — and a Sondheim favourite.

“He was here yesterday on our first day of rehearsal,” says Ms Friedman of the master lyricist and composer, a friend for years. Many of Friedman’s cabaret shows — the latest called Lenny and Steve (after Bernstein and Sondheim) — have been constructed around the maestro’s work. It must be a special kind of terror to make your directorial debut with a show written by someone so close.

“It’s like everything. When you think about it, you’re terrified of it all. When you’re doing it, you’re ‘in the moment’. The nerves come when you’re not working.”

But there must be an added burden of responsibility with a production that is co-produced by her long-time collaborator and producer David Babani of the Menier Chocolate Factory and her sister Sonia, one of the most powerful producers in the West End and Broadway. On top of that, Merrily — a show based on a 1934 play by Moss Hart and George S Kaufman — lasted just 16 performances when it first appeared on Broadway in 1981. Although there was a critically acclaimed Donmar Warehouse production in 2000, it has never played an unsubsidised West End playhouse. So no pressure, then.

“I know the piece inside out. And I know its psychological elements and its structure,” Ms Friedman says. Well, of course she does. She performed in the very production that Sondheim and Furth rewrote into the version that has been done ever since.

This latest revival comes into the West End with a superb cast but no one who is a bigger star than the show’s director. Still, if the Menier run is anything to go by, the transfer will be one the West End’s must-see productions, not just for its matchless singing but for the intelligence of the staging, which sets the show in a Frank Lloyd Wright-style Palm Springs apartment instead of the usual New York environment.

“People said: ‘It’s set in New York’. And I said: ‘No it’s not. It’s set in his [Franklin’s] head.” So this is what the director means by “psychological elements.” As Sondheim said recently, it will be interesting to see what show Ms Friedman directs next.

There is talk of two musicals and a play but she can’t say more until they are green-lit. But it sounds like the musical will be American. That’s where the vast majority of her singing repertoire comes from. Not just American, but Jewish. Why?

“There are certain chord sequences, keys and relationships to keys that are Jewish,” she says. “And that makes me feel comfortable. It’s genetic. I really do think it is.

“Because when I first sung the Vilna songs I thought I’d come home. And I had no idea there was any connection in my family to Vilna. I just thought: ‘I know how this goes.’ It felt right.”