"She sleeps with fear in her soul. She is full of terror and paranoia and insecurity. She hides it with stillness. She does not move much and that’s been a real challenge for me. I fidget. She’s like a cobra, she’s a snake just waiting and waiting… the hard thing is it’s freezing where we film [in Belfast] in a shipyard for five months a year and I’m there in a silk dress trying to be totally still."