The track from Lennon's 1971 solo album, 'Imagine', was penned after McCartney successfully dissolved the Beatles partnership in a High Court lawsuit, and after the iconic Liverpool group's frontman slammed his bandmates - Macca, Sir Ringo Starr and the late George Harrison - in an interview with Rolling Stone magazine in 1970, the year they split.

McCartney and his then-wife Linda reacted by having ads published mocking Lennon and his now-widow Yoko Ono, which saw them dressed up as clowns.

'How Do You Sleep?' was penned in response to McCartney's solo LP 'Ram', which featured the track 'Too Many People', which he later admitted intended to slam Lennon.

On his track, Lennon brought up the conspiracy theory that McCartney died, on the line: "Those freaks was right when they said you was dead."

Whilst it opens with: "So Sgt. Pepper took you by surprise", a reference to their seminal 1967 album.

What's more, the song saw Lennon claim McCartney only contributed the song 'Yesterday' to the band and referenced his solo hit 'Another Day'.

Lennon - who was shot dead in 1980 - sang: "The only thing you done was yesterday / And since you've gone you're just another day."

It's this line that hurt Macca the most.

Whilst Lennon also sang: "You probably pinched that bitch anyway", in response to Macca allegedly telling his bandmates he wasn't sure if he'd taken the melody to 'Yesterday' from another song.

Although the 'Let it Be' songwriter, 78, found the song distasteful, he has admitted that there were many people influencing the lyrics at the time, including Yoko and the band's manager, Allan Klein, who McCartney had distanced himself from.

In a new interview with GQ magazine, McCartney admitted: "I remember reading an article, an interview with Yoko, who, okay, she was a big John supporter, I get that, but in this article she goes, 'Paul did nothing. All he ever did was book the studio.'

"And I'm going, 'Err? No...' And then John does this famous song, 'How Do You Sleep?' and he's going, 'All you ever did was 'Yesterday'...'

"And I'm going, 'No, man.'"

He continued: "But then you hear the stories from various angles and apparently people who were in the room when John was writing that, he was getting suggestions for the lyrics off Allan Klein. So, you see the atmosphere of 'Let's get Paul. Let's nail him in a song...' And those things were pretty hurtful."