Background: The fifth Beatle is an informal title that various commentators in the press and entertainment industry have applied to people who were at one point a member of the Beatles, or who had a strong association with the "Fab Four" (John Lennon, Paul McCartney, George Harrison, and Ringo Starr) during the group's existence. The "fifth Beatle" claims first appeared in the press immediately upon the band's rise to global fame in 1963-64. The members have offered their own beliefs of the "fifth Beatle": Lennon was critical of individuals who claimed credit for the Beatles' success, including the individual Beatles themselves, saying in his 1970 interview with Jann Wenner, "I'm not the Beatles. I'm me.
Context: Brian Epstein, the band's manager from 1961 until his death in 1967, was instrumental in the Beatles' rise to global fame. Epstein "discovered" the band in Liverpool, saw their potential, and never wavered in his faith and commitment to them. He purposefully restricted his oversight of the band, limiting himself to business matters and public image, and gave the band free creative rein in their music. Epstein also doggedly sought a recording contract for the band in London at a crucial moment in their career, fighting their perception as provincial "northern" musicians.  Epstein's death in essence marked the beginning of the Beatles' dissolution, as Lennon admitted later. Because he was not creatively involved with the band, Epstein was only infrequently called the "fifth Beatle", but over the years he and producer George Martin have clearly been recognised as the inner circle members who most profoundly affected the band's career. In an interview in the 1990s describing Epstein's involvement in the band's rise to fame, Martin declared "He's the fifth Beatle, if there ever was one."  McCartney summarized the importance of Epstein to the Beatles when he was interviewed in 1997 for a BBC documentary about Epstein. He stated: "If anyone was the fifth Beatle, it was Brian."  In 2013 Epstein was the subject of a graphic novel entitled The Fifth Beatle by Vivek Tiwary. The book was released in November and spent several weeks on The New York Times best-seller list, reaching no. 1 in its third week of release.
Question: Who is Brian Epstein?

Answer:
Brian Epstein, the band's manager