The writer rejected Tinseltown in favour of a British TV adaptation of Labyrinth.
"When Labyrinth became a worldwide hit, we did have conversations with Hollywood but my agent and I didn't feel you could ever do it [justice] in a couple of hours," she said.
"Everyone was talking about the male lead, but the leads are women. So we turned down Hollywood."
"I have a few lines at the end," she said. "It's my first acting role and I'm comfortably sure it will be my last.
"The actors were both standing with me, looking at me as I was talking. It was an extraordinary sense of my characters coming to life."
The series, which was executive produced by Ridley Scott and his late brother Tony, will air on Channel 4 next year.
:: Citadel by Kate Mosse is published by Orion, priced £18.99. Available now.