I've spent the week in the company of The Beatles; it has been most enjoyable.

I've been wading through Mr Jackson's epic look at a month in the life of the Fab Four, spending about eight hours with them as they write, rehearse and record their Let It Be album.

It's a rare privilege really, sitting in on a session with the world's most famous group of musicians and witnessing moments of creative brilliance and intimate interaction.

You watch Paul McCartney discovering Get Back. 'Discovering” because he's got half a sorta bass line and half a sorta tune and is just experimenting. And over about ten minutes it becomes Get Back. It's a thrilling moment, a truly exhilarating experience. It's like being there to witness the big bang.

Get Back and its tangled path to creation is the high-point of part one, which covers a mere week of rehearsing. Did you know it was briefly a protest song? This was happening as Britain was rocked by anti-immigrant sentiment, with racist politician Enoch Powell riling the nation by predicting 'rivers of blood” running in the streets. The first lyrics didn't feature 'a loner” from 'Tucson Arizona” but a 'Pakistani”: it was an anthem in support of immigration.

Work

The film is also a reminder that studios are where musicians work, and work is often long-winded and repetitive. And a bit boring.

That's a basic problem. Long rehearsals, and playing songs over and over to get them right, is about as interesting as it sounds, as is the process of repeatedly playing and recording a song, and then listening to the playback.

That's essentially what sessions are like and it takes bloody forever. Even Peter Jackson's slick editing struggles to find drama, which perhaps explains his apparent affection for the boys singing in silly voices. They do that a lot. Particularly Paul. A lot. Sure, he does very good silly voices, but it does go on...

I also noticed a curious phenomenon that I've named the Reverse Yesterday.

Remember that movie Yesterday? The cute one where a guy, Jack, wakes to find he is the only person in the world who remembers The Beatles' music.

At one point Ed Sheeran (the real Ed Sheeran) challenges our hero to a 10-minute songwriting contest. Ed sings his newly-written song and then Jack delivers The Long and Winding Road, comprehensively winning and sending Ed off to bed.

Obstacles

In the first part of Peter Jackson's documentary we have something like the opposite situation. Paul McCartney is at the piano writing The Long and Winding Road, and he's stuck on the second verse. 'It needs to be another obstacle,” he says, scatting the melody and trying out various meteorological options. 'Or maybe it should be about the road again...” he ponders.

And the more it goes on the more you just want to shout at the telly: 'Wild and windy night – get a grip Paul, it's THE WILD AND WINDY NIGHT!” That's the Reverse Yesterday: the entire world knows the song except one person, and he's the one writing the damn thing.

It has to be admitted that, unless you are an absolute Beatles fanatic, this will drag. Part two certainly seems to and it's a bit of relief to get to the part three's rooftop concert. And, weirdly, despite having to sit through all those silly voices, there are actual filmed songs that made it onto the Let It Be album which we only see small excerpts from. Really?

These three films are certainly extremely long. Between them they pretty much match the running time of the entire Hobbit trilogy - and that had five armies and a desolate dragon.

But if all that sounds like too much, then just skip to the last 40 minutes of the final third. Watch The Beatles play on that roof. Even now after all this time it is a thing of beauty and wonder.

All that stuff about bands being greater than the sum of their parts – there it is, right in front of you. What a great band.