Sir Paul McCartney has long claimed that The Beatles classic A Day In The Life was about a drug-addled politician who “blew his mind out in a car”.

       The claim put him at odds with bandmate John Lennon, who said the lyrics were inspired by the car crash which killed Guinness heir Tara Browne.

       But in a new book, Sir Paul has changed his tune and said the song is indeed about the death of his socialite friend – and added, contrary to what has previously been believed, that he, not Lennon, wrote the words.

       The Beatles star makes the claim in The Lyrics, which Sir Paul describes as “as close to an autobiography” as he will write.

       The book, released on Friday, gives the personal details behind 154 songs penned by Sir Paul, including previously unknown works that were never recorded.

       It is the latest twist in the back story of A Day In The Life. Sir Paul was quoted in the 1997 biography, Many Years from Now, as saying that the song contained a verse about a “politician blowing his mind out in a car”.

       He added that the inspiration for the lyrics, which feature on the 1967 album, Sgt. Pepper’s Lonely Hearts Club Band, “[have] been attributed to Tara Browne, the Guinness heir, which I don’t believe is the case.

       “In my head I was imagining a politician bombed out on drugs who’d stopped at some traffic lights and didn’t notice that the lights had changed.”

       But in his new book written with prize-winning poet Paul Muldoon, Sir Paul states of Browne - who died in 1966 - that: “I wrote about him in A Day In The Life: ‘He blew his mind in a car/ he didn’t notice that the lights had changed.’”

       The explanation also appears to give Sir Paul credit for penning the opening section of the song, which has long been attributed to Lennon, who himself said that Browne’s fatal car crash “was in my mind when I was writing that verse”.

       Other questions have been raised about the accuracy of the many recollections in the two-volume work, as Sir Paul also states that he was inspired by Jimi Hendrix to buy his famous Epiphone Casino Guitar, which he still uses in performances today.

       He writes: “I went into the guitar shop in Charing Cross Road in London and said to the guy: “Have you got a guitar that will feed back, because I’m loving what Jimi is doing’”, adding that: “That became my favourite guitar, and I used it on the intro riff to Paperback Writer.”

       But Hendrix played solo in the UK for the first time in September 1966, having not released an album or a single under his name at that point. Paperback Writer was released in May 1966.

       It is understood that The Lyrics' publishers, Penguin, will not seek to make changes to the work, which has been shortlisted for the Waterstone’s Book Of The Year award.

       While Lennon claimed credit for the opening verse, it is understood that Sir Paul has previously given an account of co-writing the opening of A Day In The Life with his bandmate, and of newspaper clippings including stories about potholes and the death of Browne.

       It is also understood that while Hendrix’s big arrival was after Paperback Writer, his earlier and more obscure work with the Isley Brothers could have impressed Sir Paul.

       Sir Paul is candid in the book about the personal inspiration for his songs, including his mother Mary - whose visionary appearance led to Let It Be - and former girlfriend Jane Asher.

       He is also frank about his own instrumental limitations, stating that many songs were composed with his technical flaws accounted for.

       Songs included in the alphabetically-ordered book span Sir Paul’s time in The Beatles, during which he aimed to cover subject matter outside the traditional pop song themes, and with Wings.

       Sir Paul recounts in the entry for Live and Let Die that he “always had a sneaking ambition” to record a track for the James Bond franchise, but that he ultimately “didn’t rate” his own song compared to those used for Goldfinger and From Russia With Love.