For millions of Beatles fans, it was a painful chronicle of the disintegration of the band they worshipped.
Shown briefly in cinemas in 1970, the documentary Let It Be laid bare the antipathy which consumed the world's biggest pop group.
McCartney always felt it showed how the interference of Yoko Ono led to the break-up of the band, with the rest of the group ganging up on him. Lennon and Harrison, on the other hand, loathed the film - and always blocked plans for its reissue.
'John and George hated the film, which is why it's been hidden away all these years. Lennon used to describe it as "a project set up by Paul, for Paul".'
McCartney, however, believed at the time that Let It Be could help recapture the joy of the group's early years.
The documentary was filmed over one month in early 1969.
But, as enthusiasm for the project evaporated, the original idea of filming in exotic locations such as the Sahara was downgraded to shooting at the atmosphere-free Twickenham Film Studios.
When the four decided they could not face playing a proper concert for the finale, they instead performed live on the roof of the Apple offices in Central London.
By the time the documentary was released in May 1970 the party was over. McCartney had already announced he would never work with the Beatles again.
Those who saw the film were left in no doubt why they had split up - they simply did not get on any more.
Some felt the continual presence in the studio of radical Japanese artist Yoko Ono, Lennon's then girlfriend, showed the Fab Four turning into the Fab Five.
Lennon said later: 'It was hell making Let It Be - the most miserable session on Earth. It was just a dreadful, dreadful feeling being filmed all the time.'
Harrison said: ' It was a very difficult, stressful time and being filmed having a row with Paul was terrible. I thought, "I'm not doing this any more. I'm out of here". I got my guitar and went home.'