Fagin is played by Alec Guinness in that 1951 interpretation.
The main flim of Oliver! (there has been many others) Mark Lester played Oliver the street child. There have been a number of film and TV versions of Oliver Twist, and there are more closely related...
Hundreds if not thousands of actors have played Oliver, on stage and screen.
Hundreds if not thousands of actors have played Oliver, on stage and film. But The Main Musical Oliver Was Played By Mark Lester!
Fagin was played by Alec Guiness.