His name is David Prowse. He was the body actor for Darth Vader. Originally, he thought he was also going to be Vader's voice, but George Lucas thought he didn't sound menacing enough and he hired James Earl Jones to do the voice over. That ticked David Prowse off and he since did not stop complaining to the press and fans about the way he was treated by George Lucas.
This eventually led to Lucas banning him from any Star Wars fan conventions. When Prowse asked, they told him that he had 'burnt one too many bridges between him and George Lucas.' Check out a video below and tell us if you think Lucas made the right choice