John Lennon at 75: the man behind the music

It wasn't a happy beginning. Born in war-time Liverpool in 1940, John Lennon's parents - Julia and Alfred Lennon - soon separated. His father, a merchant seaman, returned with the intention of taking the young John with him to New Zealand, and the boy was forced to choose between his two parents, eventually going with his mother.

Julia proved to have a profound influence on his life - introducing him to the seminal music of Fats Domino and Elvis Presley, and teaching him to play the banjo. But it was a strained relationship, and Lennon largely grew up with his aunt, Mimi Smith. He largely lost contact with his father, and his mother died after being hit by a car in 1958.

A new beat

Lennon started his first band, The Quarrymen, in 1956 at the age of 15. It was the genesis of arguably the greatest rock group of all time: The Beatles. Both Paul McCartney and George Harrison were drafted into its ranks, alongside bassist Stuart Sutcliffe and drummer Pete Best. Sutcliffe eventually left the Beatles while they were in Germany (remaining in Hamburg after falling in love with German photographer Astrid Kirchherr), and Pete Best was later replaced by Ringo Starr.

There are very few careers to parallel that of The Beatles. From complete obscurity in 1960, within three years they were being touted as the next big thing - something they fulfilled with an all-conquering tour of the US in 1964. A reported 34 percent of the entire US population witnessed the band's performance on "The Ed Sullivan Show" that year.

The band came to dominate the 1960s both musically and culturally, releasing such seminal albums as "A Hard Day's Night" (1964), "Sgt. Pepper's Lonely Hearts Club Band" (1967) and "Abbey Road" (1969). In total, The Beatles released 12 landmark full-length albums in only eight years. They remain the best-selling band in history, having sold up to one billion albums worldwide.

But despite the success, cracks were appearing. Frustrated with the public hysteria, the band had stopped playing live by the mid-60s and - as the key songwriters - McCartney and Lennon were growing more openly competitive. Lennon's partnership with Japanese artist Yoko Ono also proved divisive. During the recording of "Let It Be" in 1969, frustrations boiled over. By 1970, The Beatles were no longer.

Working class hero

Lennon went on to enjoy a successful solo career, with his songs taking on a more potent political and social tenor. Songs like "Working Class Hero" endeavored to shake off the glitz of The Beatles by harking back to his gritty Liverpool roots. And in 1971, he released the song that came to define his career: "Imagine."

In 1980, with the album "Double Fantasy," Lennon returned to the music business after a five-year hiatus. For his return single Lennon symbolically chose the song "(Just Like) Starting Over." On December 8, a young man approached Lennon outside his New York apartment and asked him to sign a copy of "Double Fantasy" - then returned hours later to shoot Lennon four times in the back. The killer, Mark Chapman, remains in a US prison.