The Aussie star admits he wasn't used to the big freeze he experienced when he arrived on set for the action thriller - and he only hoped medics would recognise the symptoms of hypothermia before they took hold on him and the rest of the cast.
He tells WENN, "The cold in Finland was something else, but we were well looked after. The funniest thing was we got a memo about how to diagnose hypothermia in your co-worker, because apparently it's easier to diagnose it in someone else rather than yourself.
"One of the things was erratic behavior. I thought, 'S**t, we're on a movie set, so everyone is gonna be behaving erratically!'"
But, despite the extreme cold which dropped to minus-29, director Joe Wright insists his leading man was a trooper throughout the shoot: "A more precious actor and we would have had a complete f**king nightmare on our hands. There were no large Winnebagos and catering was basically set up in an old wooden hut... but Eric was incredibly game."