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After a week of build-up, The Beatles have released what's been billed as their "final song" called Now And Then.

It's been 45 years in the making - with the first bars written by John Lennon in 1978 and the song finally completed last year. All four Beatles feature on the track, which will be the last credited to Lennon, McCartney, Harrison and Starr.

And in a full-circle moment, it's being issued as a double A-side single with their 1962 debut Love Me Do.

Dr Holly Tessler a Beatles expert from the University of Liverpool has been telling Newshour how the song came together and what it's about.

(Photo shows: The Beatles. Credit: Getty Images)