Short answers, pulled from the story.
Mark Lewisohn is an English historian and biographer, born on the 16th of June 1958, known as the world's leading authority on the Beatles. Since the 1980s he has written reference books about the band and worked for EMI, MPL Communications and Apple Corps.
Mark Lewisohn's major works include The Complete Beatles Recording Sessions, published in 1988, and The Beatles: All These Years, a three-volume biography begun in 2013. The Complete Beatles Recording Sessions is a chronological diary of every session the band held at Abbey Road Studios.
Mark Lewisohn originally estimated the second volume of The Beatles: All These Years would appear in 2020 and the third in 2028. By August 2018 he said it was way too early to say when Volume 2 would be published, and no firm date has since been given.
Mark Lewisohn began writing about the Beatles in 1977 after winning a quiz at the first London Beatles convention, which led the fanzine Beatles Monthly to hire him to answer fan letters. He later said he simply found a career by becoming a Beatles expert.
Mark Lewisohn worked for years as editor and writer of Paul McCartney's fanzine Club Sandwich, edited McCartney's book Wingspan, and wrote liner notes for McCartney albums including Flaming Pie and Band on the Run: 25th Anniversary Edition.
Mark Lewisohn traced the line "Ringo isn't the best drummer in the world. He isn't even the best drummer in the Beatles" to a 1981 BBC Radio 4 episode of Radio Active, written by Geoffrey Perkins. He identified comedian Jasper Carrott as the one who spread it publicly in 1983, and a 2022 investigation by Andrew Dixon found the original on-air performer was Michael Fenton Stevens.