John Graham `` Mac '' McVie ( born 26 November 1945 ) is a British bass guitarist best known as a member of rock groups John Mayall & the Bluesbreakers and Fleetwood Mac .
John Graham `` Mac '' McVie ( born 26 November 1945 ) is a British bass guitarist . He is best known as a member of rock groups John Mayall & the Bluesbreakers and Fleetwood Mac .