How many movies have Robert Holmes and Roger Murray-Leach collaborated on?

They have worked on 5 movies together! Their first movie together was Doctor Who: The Ark in Space (1975) while their highest rated movie together was Doctor Who: The Deadly Assassin (1976). They have not worked together since Doctor Who: The Talons of Weng-Chiang (1977). They are most known for their science fiction films together.