Eddie Redmayne had "nine months of sleepless nights" while shooting The Theory of Everything.
The 32-year-old actor was so concerned about what Stephen Hawking, who he plays in the film, would think of his portrayal that he struggled to get off to sleep every evening after filming as he was too busy worrying whether or not the physicist would like the motion picture or not.
When asked how scared he was when he was making the movie, he said: "Terrified. I'd met Stephen and he was never going to say, 'I'm thrilled you're doing this, you're going to be amazing.'
"It was nine months of sleepless nights, thinking, 'Will he like it?' "
But Eddie needn't have worried too much as when Stephen - who was diagnosed with motor neuron disease aged 21 - watched the film he told director James Marsh he thought he was watching himself in some parts of the movie.