- Doing It for the Art: This was a passion project for screenwriter Anthony McCarten.
- Dueling Works:
- Released the same year as Churchill (starring Brian Cox as Winston) in the US. Churchill deals with the Prime Minister's state of mind in the days preceeding the crucial Normandy landings in 1944. Darkest Hour follows his early days as Prime Minister, as Britain faces a German invasion in the summer of 1940. Darkest Hour had a substantially better critical reception and grossed the most at the box office, and also received a bunch of award nominations including 6 oscars (with Gary Oldman winning one for best lead actor) while Churchill failed to get any award recognition.
- Also, to a lesser extent, Dunkirk, also released in 2017. While the two films were up against each other for several Academy Awards (including Best Picture), they're generally taken as complementary to one another, as they're completely different genres of film; Darkest Hour basically depicts the political maneuvering surrounding the military action depicted in Dunkirk and their consequences for the UK. (They were also released at different ends of the year, so they didn't compete at the box office.)
- Fake Brit: The Australian Ben Mendelsohn as King George VI.
- In Memoriam: The film was dedicated to John Hurt, who was supposed to play Neville Chamberlan before his death.
- Method Acting: Gary Oldman spent a year studying Churchill and his mannerisms before starting on the film. He even smoked more than 400 cigars, roughly £50 each (more than $20,000 USD). At the end of filming, he had nicotine poisoning and spent a holiday getting a colonoscopy.
- Posthumous Credit: This was prolific actor Benjamin Whitrow's final screen credit. He died in September 2017 before the film's general release.
- Uncredited Role: Taron Egerton can be seen playing a member of the general public on the platform before Churchill enters the tube in an uncredited cameo.
- Underage Casting: Extensive makeup was used to transform Gary Oldman into Winston Churchill, but to call this "aging" makeup would not be entirely accurate. In May 1940, Churchill was 65 years and six months old. Oldman turned 59 during filming.
- What Could Have Been: John Hurt was initially cast as Neville Chamberlain, in what would have been his final role. Unfortunately, his treatments for pancreatic cancer left him unable to attend read-throughs and so the role went to Ronald Pickup.
Trivia / Darkest Hour (2017)