Mark Lewisohn (born 16 June 1958) is an English historian and biographer. Since the 1980s, he has written many reference books about the Beatles and has worked for EMI, MPL Communications and Apple Corps. He has been referred to as the world's leading authority on the band due to his meticulous research and integrity. His works include The Complete Beatles Recording Sessions (1988), a history of the group's session dates, and The Beatles: All These Years (2013–present), a three-volume series intended as the group's most comprehensive biography. The Beatles and related subjects Early books Lewisohn has been writing about the Beatles since 1977, when he became a contributor to the fanzine Beatles Monthly. The fanzine commissioned him to answer fan letters after he won a quiz at the first London Beatles convention. When he began researching the band, he "found that it was a deep and rewarding history that was, for the most part, not very well researched by anybody else, so I just found a career by becoming a Beatles expert, I suppose you would say. Writing books and consulting on TV series, and ended up working for them. It's ridiculous. One thing just led to the next." His 1986 book The Beatles Live! featured a complete history of all the Beatles' live performances, in a format which Lewisohn would follow for his subsequent books. After being invited by EMI to listen to all of the Beatles' original session tapes, Lewisohn wrote The Complete Beatles Recording Sessions (1988). The book was in the form of a diary, listing chronologically every recording session the Beatles had at Abbey Road Studios. It included details such as who played on each track and how many takes were recorded in each session. The book featured an introductory interview by Paul McCartney. The Beatles: 25 Years in the Life (1988) included information on what each individual member of the band was doing on any particular day between 1962 and 1987. This book was republished as The Beatles Day by Day in 1990. The Complete Beatles Chronicle was published in 1992 and went one step further, detailing the band's entire career in the studio, on stage, and on radio, television, film and video. Lewisohn's next book was The Beatles' London, which he co-authored with Piet Schreuders and Adam Smith, published in 1994. This is essentially a guide book to all the Beatles-related locations in London,