As Gary Oldman would near the end of three hours in the makeup chair each day on the Darkest Hour set, he'd find Winston Churchill looking back at him.
"You start to look in the mirror. And I noticed I would do this thing - once I could start seeing the spirit of Churchill looking back at me, then I would start to grumble. Just sort of stuff like that. I was revving him up," Oldman said.
The 59-year-old British actor says it was his first time on a movie where he was in costume and fully ready before anybody else on set.
"So there were other actors in their robes and their rollers in their hair. But I arrived sort of as Winston, really," he said.
The film - from director Joe Wright - tracks several weeks in the summer of 1940 when Churchill became Prime Minister and was faced with deciding whether to continue fighting or negotiate with Adolf Hitler and Nazi Germany.
Ben Mendelsohn plays the stuttering King George VI, previously portrayed by Colin Firth in The King's Speech and by Jared Harris in the series The Crown.
"I didn't expect to equal Colin's performance. I didn't expect to be as good looking and have the beautiful qualities that Colin has," the Australian actor said.
"I hadn't seen Jared's performance, because again, I thought I - I didn't want to watch someone do it better than me. But you watch newsreel. That's what you watch."
Darkest Hour is set for release in New Zealand on Januray 11.