"I thought the best way to shoot the scene was to use a torch," says Davies.
"Historically we know Niels Bohr use to stride about the place, and it was difficult to get him to stop and listen.
When Heisenberg says 'he's here, he's there' -- using the pacing Bohr as an example of an electron moving in space -- I thought we'd have Heisenberg switch off all the lights in the room. This gets Bohr in the dark as he's moving about, and then Heisenberg shines a torch on him.
I tried the idea out on my Director of Photography and he said 'it'll work, but we need a steady cam.'
I then talked with the two actors and they said 'it's perfect, we can do it.'
In the end I think I cracked the scene, it's interesting and original, and I think it carries the audience."