Lennon started writing "A Day In The Life" while reading the newspaper, the Daily Mail. Two stories caught his eye, one about Tara Browne, a Guinness heir, and friend of The Beatles, who drove his Lotus Elan into a lamp-post in Redcliffe Square, London, in 1966, and a story about 4,000 potholes in the streets of Blackburn, Lancashire. McCartney then added the middle section, which was a short piano piece he had been working on previously. The two sections, which have little, if anything, in common, combine with surprising effectiveness to create a powerful and disturbing portrait of a narrator so consumed by the distractions of his everyday life that he is equally unmoved by a tragic car crash, a brutal war film, and the story about potholes, each of which is recounted in the same trivial tone. At the end of the otherwise fairly upbeat album, this sudden note of profound fatalism is rather startling.
The two sections of the song were separated by 15 bars ending with an alarm clock triggered by assistant Mal Evans, that, at first, the Beatles weren't sure how to fill. Then they had the idea of bringing in a full orchestra and having them "freak out" for 15 bars. The trouble was, classical musicians were not sure how to "freak out" musically. So producer George Martin had to write a "freak out" score for the musicians to follow. The sessions were filmed, but the film remains unreleased in its entirety. Portions of it can be seen in the "A Day In The Life" promotional film, including shots of studio guests like Mick Jagger, Marianne Faithfull, Keith Richards, Donovan, Patti Boyd Harrison and Michael Nesmith.