Baker portrayed the famous robot in 1977's Episode IV — A New Hope, as well as its sequels The Empire Strikes Back and Return of the Jedi and the prequel film trilogy.
According to Wookiepedia, before director George Lucas hired Baker to climb inside the R2-D2 suit, Baker was "a circus and cabaret performer with entertainer Jack Purvis," and his other film credits include Willow, Labyrinth and The Elephant Man. He was also an accomplished mouth organ player and had an act in stand-up comedy.
"It was expected, but it's sad nonetheless," Baker's niece, Abigail Shield, told the Guardian. "He had a very long and fulfilled life. He brought lots of happiness to people and we'll be celebrating the fact that he was well loved throughout the world. We're all very proud of what he achieved in his lifetime."