Funny girls Joan and Barbra take Highgate by storm

"She's such a big expressive character, every night is like a workout," says the former Fitzjohn's Primary pupil.

Roy Smiles' zinging comedy The Funny Girls Upstairs at the Gatehouse Theatre imagines a fictional early career stand-off between Rivers and fellow Jewish superstar Barbra Streisand.

Rosanna Harris plays Barbra Streisand in The Funny Girls (Image: Mark Senior)

"It's fast paced and really fun. We bounce off each other - our dressing room has been abuzz, we can't believe we are playing Barbra and Joan." adds the 26-year-old, who grew up in West Hampstead and also attended Northbridge House School.

In the late 1950s, the rising talents are pegged to duet in a taboo-busting lesbian play. But while the turbo-ambitious Rivers wants to impress her agent, Streisand is terrified of her overbearing mum in the front row.

And Rosanna Harris as a nervous Barbra even gets a first act number, surprising the ballsy Rivers with her "belting voice."

"It's written as a bit of a farce. They did do an off Broadway play together - there's a picture of them rehearsing - but they had no dialogue together and there was never a lesbian narrative. This is what Joan wanted to have happened, and it's funnier. Joan's desperation to go on because she's got an agent in, and Barbra finding it impossible because of her judgmental Jewish mother."

Smiles takes full advantage of the pair's clash of ego and wit. And as the second half revisits them a decade later, there are undertones of troublesome beauty standards and hard won female success in 60s America.

Mia Tomlinson and Rosanna Harris, The Funny Girls (Image: Mark Senior)

"I love Joan Rivers so I came to this thinking 'it's an exciting challenge, just go for it," adds Tomlinson.

"But you have to keep developing. Luckily Joan wrote autobiographies and there is so much footage of her I have not been short of inspiration, but performing her on stage is a feat. I don't look like her so are you seeing someone who is impersonating Joan or recreating her energy? I always ask 'what would Joan have done?' If she was watching would she be happy with how I'm portraying her?"

Tomlinson says the first half offers glimpses of the star's self-deprecating acerbic wit: "She's not yet fully formed but in comic moments you see hints of her stand up, and get a taste of her world view and how misunderstood she was."

And Tomlinson, whose previous jobs include pirate Anne Bonny in Netflix drama The Lost Pirate Kingdom and an alcoholic teen in Britbox's The Beast Must Die, now appreciates the complex character of a comedy pioneer who was the first woman to host a late night US TV talk show.

"She was ambitious. She had so many knocks in life but she drove forward. I think she loved the limelight and being loved. She was groundbreaking but she never felt acknowledged for it, there was this constant battle to be told 'you are brilliant you have nothing to worry about'. She always considered herself ugly, Edgar her husband never called her beautiful and that weighed heavily. She never got a job because of her looks and had to earn her place."

The Funny Girls runs Upstairs at the Gatehouse in Highgate until November 21.