The Beatles: The long and winding road to the Fab Four’s break-up

The lawsuit was a tricky balancing act for McCartney according to litigation PR expert Coad.

“When striking a deal, keeping your reputation is as important as the financial deal. The last thing Paul McCartney would have wanted was to lose his image as a loveable Beatle.”

He added: “Lots of bands were ripped off in the ’60s and ’70s.

“Bands made their money with song-writing royalties so who got the song-writing credit was very important. Take Queen for example: Brian May Freddie Mercury and Roger Taylor were concerned that John Deacon was missing out because he had not written songs.

“Very early on, and very wisely, all songs written by John Lennon or Paul McCartney were known as Lennon / McCartney songs to avoid arguments.”

However the break-up ruined the harmony between Lennon and McCartney.

On McCartney’s second post-split album Ram (1971) the song “Too Many People” included a swipe at Lennon and his partner Yoko Ono, whose presence was resented by the band.

The line “You took your lucky break and you broke it in two” was interpreted as a dig by McCartney, who later said stunts like Lennon and Ono’s “bed-in for peace” protest in Amsterdam “got up his nose”.

Lennon riposte was How Do You Sleep? on the Imagine album, with its barb “The only thing you done was yesterday / And since you’ve gone you’re just another day.”

Harrison had already written about Klein, the break-up and its aftermath in his song Beware of the Darkness, from his hugely successful and critically acclaimed first solo album, the prophetically titled All Things Must Pass.