Director Sam Taylor-Johnson consulted her friend Sir Paul McCartney about the script. McCartney said that John Lennon didn't really ride on the top of the double-decker bus like he does in the script. He also revealed that the character of Lennon's aunt, Mimi Smith, wasn't as mean and vitriolic like she was written in the script. Furthermore, the song "In Spite of All the Danger" wasn't written as an ode to Lennon's mother as the script suggests. In the end, they agreed that it's a movie rather than documentary, so Taylor-Johnson made inferences that weren't always there.
Although this movie is about John Lennon, best known for being the founding member of The Beatles, the band's name isn't mentioned throughout the whole movie.
This movie's (limited) theatrical release date in the United States was October 9, 2010, what would have been John Lennon's 70th birthday.
In the scene where John looks at himself in the mirror after he asked Mimi for his birth certificate, an actual photo of John Lennon as a youngster is seen on the fireplace mantel.