How many movies have Ian McKellen and Philippa Boyens collaborated on?

They have worked on 6 movies together! Their first movie together was The Lord of the Rings: The Fellowship of the Ring (2001) while their highest rated movie together was The Lord of the Rings: The Return of the King (2003). They have not worked together since The Hobbit: The Battle of the Five Armies (2014). They are most known for their adventure films together.