Mark Lewisohn 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, a history of the group's session dates, and The Beatles: All These Years, a three-volume series intended as the group's most comprehensive biography.