New Delhi, April 16 -- Ian McKellen and Michaela Coel met like their characters in "The Christophers" do, with a knock on the door.

Coel, taking a break from writing her upcoming BBC-HBO series "First Day on Earth" in Ghana, turned up at McKellen's house in London to go over the script with him and screenwriter Ed Solomon.

"I walked into your house," Coel recalls in an interview alongside McKellen. "I knew who you were. You were like, 'Hello! What are you? What are you then?'"

"You looked interesting and beautiful," says McKellen, smiling. "And you are."

On-screen chemistry can be elusive, especially when two characters are intended to be diametric opposites. In "The Christophers," McKellen stars as the artist Julian Sklar, a David Ho...