Now with Remembrance Day approaching, Brendan Gleeson takes on the enigmatic character in a new BBC Drama, Into The Storm.
The feature-length production, which is the sequel to the 2002 film, The Gathering Storm, has already received 14 Emmy nominations and saw Gleeson walk away with the award for Outstanding Lead Actor in a Miniseries or Movie.
But if Gleeson had let his fear take control, he wouldn't be clutching his Emmy now.
"There was never a real 'Yeah! I definitely want to go and act in that', I was very worried about it to be honest!" Gleeson, 54, confesses.
With Churchill as such an icon, Gleeson was unsure whether he'd be able to do the character justice: "I didn't know if I was going to be able to do it or whether it was a bridge too far. I wasn't sure what my relationship with this character could be. So, we did a camera test at the outset - for both me and the producers, to see whether me playing Churchill was just a daft notion."
Pleased with the outcome, he agreed to the role but he was still suffering with pre-film jitters.
His biggest concern was whether he'd be able to hide his Irish accent and be believable as the wartime Prime Minister - during the worst days of the Second World War.
"My voice coach was my saviour. She came over to Ireland and worked with me for two weeks. At the beginning of the first week, she asked me whether I was looking forward to the role. I said: 'Absolutely not! I have a ball of dread in my stomach and I don't think it will go away and I don't believe a word coming out of my mouth!'"
Luckily for Gleeson, his acting experience kicked in and he soon found he was improving: "By the second week I had a little run where I thought, 'Actually I kind of believed that', the real test was whether I was able to get hold of Churchill's private intimate voice. It had to be perfect otherwise it wasn't going to work. That's where the terror was."
Once Gleeson had overcome the accent barrier, he then had to tackle his own opinions of Churchill.
In 1991, Gleeson portrayed Michael Collins in the film The Treaty. An Irish politician, Collins battled with Churchill in 1921 over the Anglo-Irish Treaty. Gleeson found it hard to put his previous acting allegiance behind him.
"I knew how it felt to be on the other side of Churchill's wrath and will. I was wondering, 'Why am I taking this role?' I knew I'd have to shed some baggage if I was going to do it honestly."
"It was very interesting having played Collins who was sat facing Churchill across the table in The Treaty and then just to switch chairs. It's like an old acting exercise, where people have to switch roles. When you're in someone's corner, you've got to fight for them. I had to leave behind some pre-conceptions."
However, as Gleeson delved further into Churchill's character, his respect for the leader grew.
"His faults really were his strengths and his strengths really were his faults. He had a bull-headedness and determination to push things through. If you're on the end of it, it doesn't feel too good. If he's actually stopping a savage like Hitler it's pretty fantastic to have him on your side," Gleeson says.
His praise for the Prime Minister doesn't end there: "He was so witty and bold - even when things didn't go well. He was jilted by his parents a little bit and he reacted with no self pity and that then became part of his life."
"He was jilted by the American President Roosevelt when Stalin [Soviet leader] became involved and there was still no self pity. At the end of the war, he was jilted by the electorate but he came back and became Prime Minister again. That was one of his enduring qualities, he could take a blow that floored him and get up again."
The film addresses how once the war was over and the troops returned home from war, Conservative Churchill didn't publicly pursue a welfare state like the Labour party did - a move which lost him his job. Yet Gleeson doesn't think he lost the connection with the British population. "Going through the Blitz and talking to people gave him a fantastic common touch but at the same time, he did like the hierarchy structure that was in place and thought that fundamentally it worked. He introduced social reforms in the early years and was very conscious of the fact he wanted to treat people fairly, but he was part of an old order."
Looking back at the end result of Into The Storm, despite his initial trepidation, Gleeson has proved his worth as the charismatic leader. And, it seems, Gleeson has been on a steep learning curve as he finishes: "It's a great liberation to say that somebody absolutely saved the world. That's what Churchill did. There's no denying it. He was a flawed human being who achieved extraordinary heroism."
Extra time - Brendan Gleeson
For the role of Churchill, Gleeson had to shave his head and put on weight, "which I never lost, which was kind of irritating", he explains.
The Dubliner didn't begin his film career until aged 34 when he took on the role of Michael Collins in the film The Treaty.
He plays Mad-Eye Moody in the fourth and fifth Harry Potter films.
His son Domhnall Gleeson has followed in his father's footsteps and is an actor.
Gleeson will make his directorial debut in the 2010 production At Swim-Two-Birds.