It’s unusual to find two family members in the same play, let alone three. But when Janet Prince began assembling her production of Christopher Durang’s parody plays, she found herself sharing the stage with her nephew, and taking comic direction from her husband.

Janet Prince is a striking woman. Slim, with a shock of long white hair and a contagious smile, she is the force behind a new production of Durang Durang, comprising three one-act plays by New York writer Christopher Durang. Her husband is acclaimed British comedian and star of Whose Line is it Anyway Stephen Frost.

Prince met Frost when she auditioned him for his first acting role in theatre. “Apparently I put my hand on his knee,” she laughs. “I admit nothing.” But Frost quickly confirms: “She did! I’ve been sleeping with my casting director for 30 years.”

Husband and wife went on to work together in a number of shows, including Anthony Minghella’s first play. But this is the first time Frost has taken a directorial role. “I don’t take direction from Stephen very well,” admits Prince. “I always think, ‘Oh, it’s just my husband. He can’t tell me what to do’. But I’ve matured now.” Indeed, Frost has been integral to the comic timing of the three plays. “He’s put in some really great stuff,” says Prince. “I knew nothing about the ‘rule of three’ for getting laughs. He makes the tweaks and suddenly a line is funny.”

To make the family connection even more interesting, Dan Frost, Stephen’s nephew, appears in Durang Durang fresh out of another play: Stalag Happy, which tells the story of his grandfather (Stephen’s father) the late abstract artist Sir Terry Frost. “They look so similar, Dan and my father,” says Stephen. “Same voice, same face.” Dan adds: “It was a strange experience. I had my dad there and I was playing his dad. And of course Steve, who I’ve always looked up to. I thought, ‘Bloody hell. How did I get into this!’”

The trio recount further stories of their intertwined careers – “Poor Dan has been tied up by his uncle and molested by his auntie!” says Prince – finishing each other’s sentences and bantering between themselves. And suddenly it becomes clear why the bond has been so successful on stage. “There’s a level of understanding, a hidden language that works really well,” explains Stephen. “Although we barely know we’re doing it.”

All three are unfailingly complimentary, although Prince does admit that she finds taking criticism from Stephen “interesting”. Nevertheless, she stresses: “The play certainly would not have been what it is without him. Take one line in the play: ‘Is there a piano in here?’ That line wasn’t funny before. And now it’s hilarious.”

But the banter has taken hold. Stephen shoots back: “That’s because I gave you a big red nose!” The interviewer is forgotten. And just like that the three actors revert back to being, simply, the Frost family, laughing together on a Saturday afternoon.

- Rebecca Burn-Callander

Durang Durang continues at the Jermyn Street Theatre until 15 February.