Mark Lewisohn knows the Fab Four better than they knew themselves. The expert’s tapes of their tense final meetings shed new light on Abbey Road – and inspired a new stage show

The Beatles weren’t a group much given to squabbling, says Mark Lewisohn, who probably knows more about them than they knew about themselves. But then he plays me the tape of a meeting held 50 years ago this month – on 8 September 1969 – containing a disagreement that sheds new light on their breakup.

They’ve wrapped up the recording of Abbey Road, which would turn out to be their last studio album, and are awaiting its release in two weeks’ time. Ringo Starr is in hospital, undergoing tests for an intestinal complaint. In his absence, John Lennon, Paul McCartney and George Harrison convene at Apple’s HQ in Savile Row. John has brought a portable tape recorder. He puts it on the table, switches it on and says: “Ringo – you can’t be here, but this is so you can hear what we’re discussing.”