Most of New York playwright Alix Sobler’s work is set in north America, and although she is not entirely happy with such labels, much of it is Jewish.

For instance, her first play to open in London, in 2016 at The Finborough, was called The Great Divide and was based on one of New York’s deadliest fires which in 1911 killed 146 factory workers, most of them Jewish immigrants. Then there is The Secret Annex which imagines Anne Frank surviving the war and follows her attempt to get her memoir published. Sobler’s dark and topical plays have been performed across the US and also Canada where she lived for ten years winning the Canadian Jewish Playwriting Competition in 2015.

But her latest play is about a 19th century Bavarian princess. It feels culturally and geographical very far from home. In fact, Sobler seems the least likely playwright to have written it when you only know of the subject matter.

“I think it’s one of those things where, if you know I’m Jewish and you look for it, you’ll find it,” says Sobler about her work generally. But it is even truer of this play about the real life, bizarre case of Princess Alexandra of Bavaria who believed that she had swallowed a glass piano.

Set in a palace in which the princess and her father King Ludwig, a failed poet, live a life of splendid if dysfunctional, isolation, Sobler’s sharp, witty writing delightfully subverts the pomposity of royal etiquette.

“One of the things I’m interested in is historical stories that go a little bit less noticed because they are about women, or people of colour, or about poor people,” says Sobler who is in London for rehearsals. She lives in New York with her Canadian husband and two cats.

To be clear, the piano in Sobler’s play is no dainty little ornament, but a full-sized grand. Even more strangely, Alexandra’s belief that she swallowed one was by no means the only case in which a member of European nobility believed they had consumed the instrument. From the Middle Ages this debilitating psychosis known as “the glass delusion” was known to afflict people of royal standing and was by no means rare until it fizzled out in the 19th century. But in Sobler’s play, which on the page, at least, is easily funny enough to be called a comedy, Alexandra’s condition is a way of exploring all sorts of themes. “There is a lot that can be said about the actual condition she suffered from because she’s a real person,” says Sobler. “But I take it as a jumping-off point. I suffer from anxiety. And anxiety is the state of being Jewish. It is a play that deals a lot with isolation and feeling very different.”

This not to say that anxiety is a uniquely Jewish phenomenon, Sobler is keen to add. But there is something particularly Jewish, she says, about writing about people who have been lost. Take Philip Roth, Wendy Wasserstein or Arthur Miller, by way of examples.

“Miller is interesting because I think he often wrote around being Jewish, but his work is to me very Jewish. The work is full of ghosts. I recently adapted a Yiddish play. It’s all about immigration and sex work and exploitation of workers. But really it’s so full of ghosts too. I think the whole culture of Judaism is about story telling, and that’s what intrigues me about so many stories.”

Yet as seriously as Sobler talks about her work, much of which is driven by a sense of social justice and feminism too, it all tends to be framed within a comic sensibility.

“My work is all comedic,” she says breezily. “A lot of my humour comes from my Jewish background. And it’s one of our points of pride because we keep our humour in very dark circumstances.”

Her family are “hilarious”, she says. Her orthodontist father Terry is very funny, and so too is her brother Ian (also an orthodontist) who is funny in a “visceral” way. “And my mother, who is dead now, was also very funny but in also an amazing audience. We laughed through some very difficult times. She suffered greatly with cancer and died about 15 years ago. It was a brutal experience. But she never lost her sense of humour, which I know is a banal thing to say, but it was true.”

Humour even informs what Sobler calls her “Holocaust plays.”

As well as her Anne Frank play there is one called Sheltered about an American couple who travel to Europe to save children on the eve of the Holocaust, the first act of which takes place in the US at a dinner party.

Her adaptation of The Golem is set in the Warsaw ghetto where a group of actors perform the play.

“For me, if I can’t laugh, that’s really not a life worth living.

“And that’s why dark stories and sad stories are often the funniest.”

Yet the themes explored in The Glass Piano are more personal than cultural.

“The metaphor was so strong for me about what it means to feel fragile, and so vulnerable that you can’t approach other people. I think I can really relate to that. And it spoke to me of the 21st century and the way we find ways to insulate ourselves from each other.

“The play is also about mother loss because Alexandra’s mother isn’t there any more.

“In Alexandra’s case it’s because her mother left, in my case it’s because she died.

“But the play reflects that anxiety a lot,” says Sobler who, thinking about it, is exactly the right person to have written this play.

The Glass Piano is at The Print Room from April 26 – May 25.

www.the-print-room.org