Oscar winner Steve McQueen had long wanted to make a movie about the Blitz - Germany's wartime aerial bombing of British cities - but it was seeing a photo of a Black boy waiting to be evacuated that inspired him to explore the theme through a child's eyes.
His film "Blitz" is based on thorough research and true events, the British director of "12 Years a Slave" and "Hunger" told Reuters in an interview.
While researching another project, he came across the photo of the boy at a train station - one of hundreds of thousands of British children to be evacuated from towns and cities during World War Two.
The film stars Saoirse Ronan as Rita, a Londoner who sends her son George, played by newcomer Elliott Heffernan, to the countryside for safety during the war. But George is determined to return home despite the dangers ahead.
Many of the characters and events George encounters are based on extensive research and documented by author Joshua Levine, who joined the project as a historical adviser, said McQueen.
"I thought, 'you've got to get it right'," McQueen said.
"In fact, the research sort of just propelled me and inspired me to the story and George's odyssey through London at that time. It was exciting because you found all these characters, all these facts, which most people unfortunately didn't know, and you want to sort of illuminate them on screen."
The Blitz - from the German word Blitzkrieg, or "lightning war" - lasted from Sept. 1940 until May 1941. For Britons it conjures up images of Londoners huddling in underground shelters and rallying to battle blazes and rescue people from the rubble.
McQueen said he had discovered a diverse, "quite cosmopolitan" London through his research.
"There was a large Chinese community and there was a Black presence. There was all kinds of presence here in London. I wasn't trying to push some kind of narrative. It was just what one found within the sort of everyday of London," he said.
Like George, 11-year-old Heffernan embarked on a transformative journey with the movie.
"It was a big adventure being on my first film, seeing how films are made and going out on different locations," said Heffernan, who was nine at the time of shooting.
The movie also proved new territory for four-time Oscar-nominee Ronan, who spent months working with a vocal coach to prepare for scenes which see her singing live.
"It's the kind of thing I've always been terrified to do in front of everyone, but I've always wanted to do it," Ronan, 30, told Reuters.
"It was incredible to see how strong you can become at something that you're just not a professional at after a few months. It gave me a lot of confidence."
"Blitz" is out in select cinemas on Nov. 1 and will stream on Apple TV+ from Nov. 22.