Source TCA Press Tour 2011
During the Q&A, Green and Fiennes said they were very excited about their characters' dynamic, with Green noting, "Morgan hates Merlin, because also he's put Arthur on the throne. But she also kind of respects him. She enjoys toying with him like a cat with a mouse."
Fiennes described the back and forth between the two as, "Villainous antagonism. It's a fulfilling place to be. There's great chemistry. It's essentially good and bad, but you realize where her evil roots stem from. Merlin is sort of Machiavellian in his architectural bring about of this young king. He walks with a very dark shadow as well."
On the other hand, Green said that when it came to the two magicians, "Their relationship with magic is quite different," remarking that while Merlin is "world weary about magic," for Morgan, "Magic is new to her. She's drawn to it. It's very exciting, like a drug."
Asked about the appeal of these sort of period pieces, Bower replied, "A key love story. I think people are fascinated with the relationship between Guinevere and Arthur and almost the bizarre sexual chemistry between Morgan and Merlin."