Gary Oldman's long wait for an Academy Award could finally be over following his widely acclaimed performance in Darkest Hour.

The film, from director Joe Wright, sees the 59-year-old Londoner take on the role of Winston Churchill, Britain's iconic World War II prime minister, and he has already been nominated for a Golden Globe, an early indicator of potential Oscar recognition.

Oldman - whose only Oscar nomination to date came courtesy of 2011's Tinker, Tailor, Soldier, Spy - is utterly transformed as Churchill, having spent 31/2 hours daily on the make-up chair during the film's production as he was fitted with extensive prosthetics for his body and face.

Making Darkest Hour, he says, proved the most difficult role of his 35-year career.

"This was the hardest job I've ever been on as an actor," he says. "Initially, my concern was stamina because Churchill is in almost very scene and is the engine of every scene.

"I was working every day, coming in four hours before everyone else and going through that process. My day was about 18 hours by the time I'd got home and had dinner.

"There are worse things than that in life, of course - I am not complaining - but all that was a concern for me. I wondered if my skin would hold up (under the prosthetics). Yet it was also a very freeing role."

Surprisingly, Darkest Hour is Oldman's first role as a leading man since Tinker, Tailor, Soldier, Spy.

In the interim, he had taken on supporting roles in the likes of The Dark Knight Rises (2012), Dawn Of The Planet Of The Apes (2014), Child 44 (2015) and The Space Between Us (2017).

"And the lifting is a lot easier when you are a supporting character and you are having rest days and are coming in and out," he says with a smile.

In Darkest Hour, Oldman does plenty of lifting, starring in almost every scene while standing at the centre of a narrative that tells of the fraught days in parliament during the opening weeks of World War II, as the British government sought a strategy to cope with the onslaught unleashed by Nazi Germany.

Hitler's blitzkrieg, or "lightning war", obliterated Poland's resistance, while France and the Low Countries buckled in a matter of weeks, leaving Britain's entire fighting force trapped in France and facing a perilous fate.

Inspiring the near-miraculous recovery of British troops from Dunkirk, the newly appointed Churchill looked to the British people to inspire him as he stood firm and fought for his nation's ideals, as well as Europe's liberty and freedom.

The film seeks to look behind the curtain, revealing the man disguised by the public persona, and this was one of the film-makers' greatest challenges - for all Oldman's experience playing real-life figures, ranging from Sid Vicious (in Sid And Nancy, 1986) to Lee Harvey Oswald (JFK, 1991) to Beethoven (Immortal Beloved, 1994).

"Churchill's public image is a very specific one," says Oldman. "He was a self-promoter and he understood the sense of branding before branding was even a thing."

He points to Churchill's outfits, the homburg hat, scarf and his Victorian-style suit with a bow tie and a fob watch.

"There was a sense of theatre and presentation about him," the actor says. "He wanted to appear bigger than life. There is a grandeur to him; he is like a performer. Joe and I wanted to see the human side of him, pushing through all of that to find the man beneath."

The actor and the director were aided in their quest by the two primary supporting characters, Churchill's wife of 31 years, Clemmie (Academy Award nominee Kristin Scott Thomas), and his tireless secretary, Elizabeth Layton (Downton Abbey star Lily James). Churchill's relationship with his wife reveals a surprising tenderness while his interactions with Layton demonstrate both his meticulousness and his bright sense of humour.

"Churchill uses humour as a defence and as a way of navigating the difficulties in life, as we all do," says Oldman. "That's the reason why humour is mostly about sex and death, because they make us most uncomfortable.

"The most interesting research was reading the writings of people like Elizabeth Layton and discovering that they all described him as having laughter just behind the eyes," he adds. "Churchill was waiting to go into laughter at any given moment and they found that lovely and refreshing."

The film seems timely, especially to European audiences, who are entering a period of uncertainty with the United Kingdom's departure from the European Union, and to American viewers, many of whom worry about the quality of their political leadership.

Oldman and Wright, however, do not regard Darkest Hour as a polemic. It is concerned with the life of a famous politician, but is not overtly political.

"We started work on the film in January 2016 so Brexit hadn't happened and Trump hadn't happened," asserts Wright, who returns to World War II for the second time following his success with Atonement in 2007.

"The European elections in the rise of the Nationalist sentiments in Europe hadn't happened. As we made the film, these things did begin to appear and there was a temptation at one point as we were developing the screenplay, to invest the film with our kind of political point of view. I tried, in fact, at one point."

Wright was intrigued by the fact that Churchill had been one of the first people to talk about a European Union. "And that was amazingly perceptive of him. I added a line where Churchill was looking out of the window and said something like, 'This can't go on. We must form a European Union.'

"But it just reeked of the author and it took me out of the film, so we realised very early on that we had to be specific about this very specific character at this very specific time facing this very specific enemy. The most I could hope for as a film-maker is that the film raises questions for people and starts the conversation."

The film has already raised questions and sparked conversations, not least about its leading man's candidature for an Academy Award. Certainly, his director is full of praise.

"When I heard, 'Gary Oldman portraying Winston Churchill,' I thought, 'What a performance that will be to witness,'" says Wright. "He has been my favourite actor since I was a teenager, from Sid And Nancy to Prick Up Your Ears (1987) to The Firm (1989)."

For all the plaudits he has received, however, Oldman remains unfazed.

"Everything thus far I have played has always been incoming work," he says. "And roles like this one don't come along very often so I don't engineer a great deal of it. I have no clue what I am going to do next year."

He laughs. "Mostly, I am out of work."