John Lennon
As The Beatles they had written the rulebook in the 1960s, setting standards of artistic and commercial success that other rock bands could only hope to imitate.
So it was that when it came to breaking up, they were once again in virgin territory. There were no examples of "solo careers salvaged from supergroup break-ups" for them to follow. No Robbie Williams, no Peter Gabriel, no Michael Jackson or George Michael.
A giant question mark hung over the respective futures of John, Paul, George and Ringo.
Expectations were highest of the leading songwriters, John Lennon and Paul McCartney.
John Lennon
Lennon was increasingly preoccupied with his new wife, Yoko Ono, with whom he had already launched a campaign for world peace. The pair teamed up with producer Phil Spector to cut Lennon's first post-Beatles album, an introspective, cathartic affair titled John Lennon/Plastic Ono Band.
In 1971 Lennon decamped to the United States where he remained until his death in 1980. The same year he recorded his best-known solo track, Imagine.
Still charged with bitterness over his fall out with McCartney, music proved a fruitful outlet. Although Lennon's solo output was patchy, it boasts awesome works including Jealous Guy, Whatever Gets You Through the Night and Mind Games.
By the mid to late 70s he had put the rock and roll excess behind him and become a doting father to his son with Yoko, Sean.
In December 1980, shortly after his return to musical form with the album Double Fantasy, Lennon was assassinated outside his New York flat.
Paul McCartney
McCartney, always more straightforward than Lennon, saw the break up of the Beatles as a chance to settle down and enjoy family living with his new wife, Linda.
Yet critics said the lack of inner turmoil meant his solo offerings lacked the emotional weight of Lennon's post-Beatles material.
McCartney sought to put the glitz and glamour behind him. With Linda he formed a new band, Wings, which enjoyed commercial success with tracks such as Live and Let Die, Jet and Band on the Run.
A master melody writer, he was never far from a hit single. Mull of Kintyre, Ebony and Ivory (a collaboration with Stevie Wonder), Tug of War and Pipes of Peace were among his chart successes.
Never content to rest up, he wrote and starred in the film Give My Regards to Broad Street, appeared at Live Aid, penned the much scorned Frog Chorus and composed the classical works The Liverpool Oratorio and Standing Stone.
In the mid 1990s he joined Harrison and Starr for a Beatles reunion, and was knighted by the Queen in 1997.
Linda's death the following year from breast cancer saw McCartney retire from the spotlight for more than a year. He recently returned with a new album of cover songs, Run Devil Run.
George Harrison
Outshadowed by the Lennon-McCartney partnership, the break up of the Beatles was seen as a chance for George Harrison's formidable songwriting talent to shine.
In fact he never managed to match his finest Beatles songs, Here Comes the Sun, While My Guitar Gently Weeps and Something, which Frank Sinatra praised as one of the best love songs ever written.
In the 80s he indulged his passions for racing cars and cinema, helping set up HandMade Films, which spawned triumphs such as The Long Good Friday and Withnail and I.
Of all the Beatles, Harrison was most convinced by their dalliances in Eastern religion. He remains a keen exponent of transcendental meditation and has invested time and money in the Natural Law Party.
Ringo Starr
When it came to going it alone, Ringo Starr appeared to be the most insecure of all the Beatles. Never a dedicated songwriter, Ringo instead decided to "get by with a little help from his friends".
His 1970s solo albums, Ringo and Goodnight Vienna, featured a rollcall of celebrity musicians including his former bandmates.
But drink and other lifestyle problems got in the way and Ringo spent much effort getting back on the straight and narrow. Recently he has toured and recorded with his All Starr Band.
His dulcet Scouse tones are familiar to many children around the world as the voice behind the television series Thomas the Tank Engine.