The star, 32, says she cannot stop giggling when the cameras roll – known as “corpsing” – and many scenes are being left on the cutting-room floor.
She said: “I have got seven kids at the moment on screen. We’re filming scenes with seven children. They’re absolutely hilarious and the bloopers are so brilliant. I’m terrible because I just corpse.
“It really takes its own completely different life where they run around and go and sit on the throne mid-scene.”
Queen Victoria and Prince Albert had nine children in total – four boys and five girls born between 1840 and 1857.
Jenna also plays a mother in a new BBC One thriller series, The Cry, in which her character’s newborn baby is abducted in Australia.
She said: “I play Joanna, a new mum struggling with motherhood. She feels exhausted. “She feels like she’s lost her identity and she’s struggling to connect with Noah. That’s where we begin.”
However, she said the twin babies who played her son were much better behaved than her co-stars in Victoria.
She said: “We’ve had five weeks filming with them. They were like these magic, genius actor babies who seemed to know what the word action meant and what the scene required.”
The Cry, tonight, BBC One, 9pm.
