Actor Timothy Spall told Sky News he was hesitant about taking on the role of Irish unionist Dr Ian Paisley for a new film.
The Harry Potter star plays the politician in The Journey, which imagines a conversation between the founder of Northern Ireland's Democratic Unionist Party and his political opposite Martin McGuinness from Sinn Fein.
The discussion resulted in the 2006 St Andrews Agreement, which ended Ireland's bloody civil war.
Spall admits he had doubts about the role.
"Yeah I did, enormous. For a start I thought I never saw that coming round the corner, I never thought that I would be in the frame for something like that, but then I was incredibly intrigued by it," he said.
"Slightly afraid of it because I thought this is such a sensitive subject. And when I get afraid of something and then I start fearing it I think well it's a challenge."
"So I swallowed all that, took a deep breath, checked out a few things - that I wasn't going to upset anybody hopefully. And I went ahead."
Star Trek actor Colm Meaney plays McGuinness and agrees that the role took some consideration.
"Having read the script and being very moved by the script, and impressed by the writing in that it humanised people that are often demonised and I think gave a great insight in to the incredible complexities of the political situation in the north of Ireland," Meaney said.
"Having been impressed by the script I was also very aware of the pitfalls, the dangers and just as Tim said, being very, very careful about it."
Spall underwent a physical transformation for the film but says it was understanding Dr Paisley's mindset that was the real challenge.
"I bleached my hair white so I didn't have to wear a wig all the time. Luckily the consistency of our hair was pretty similar so that was always pure white, and they give me some teeth because Dr Paisley had a good set of choppers on him, and they give me a bit of a chin," he told Sky News.
"Also he was about a foot taller than me so I was wearing raised shoes at the time," he added.
Meaney says the role took on a new meaning for him after McGuinness's death in January.
"It's very sad that Martin has passed and I feel very differently - I knew him, not well, it's very sad and he's a huge loss. As Dr Paisley was when he went." Meaney said.
"They embodied that revolution that led to the peace protest, and losing Martin especially with things so up in the air as they are again in Northern Ireland, it's a shame to lose him, to lose him so young."
The film received a standing ovation after it was shown at the Venice Film Festival last September and will open in cinemas here this week.
Meaney says he's looking forward to seeing how it's received in Northern Ireland.
"I think anybody who has shared, or been aware of the journey these guys made, would be open to the film, and hopefully that's the majority of people," he said.
"I think we're always going to get some blowback from entrenched opinions and that but that's part of the territory, you expect that. But one would hope the general response would be that they'll enjoy the film as well, it's a celebration of what was achieved."
The Journey is out in cinemas in the UK on 5 May.