Which actor played Gandalf in 'The Lord of the Rings' and 'The Hobbit' trilogies?

Ian McKellen played Gandalf in the six films of the trilogies 'The Lord of the Rings' and 'The Hobbit' directed by Peter Jackson. Curiously, Sean Connery turned down the role because he didn't understand the script, and Patrick Stewart couldn't accept it due to conflicts with 'X-Men'. McKellen was on the verge of turning down the role of Magneto in 'X-Men' to avoid conflicts with 'The Lord of the Rings'.