There are many who believe Colin was accepted as Merlin on the first audition. It’s a wonderful idea; however, Julian Murphy and Johnny Capps were looking for someone who could portray more than a one-dimensional character … they were looking for an actor with presence and skill who could portray many different emotions … many different aspects of a complex character. One audition would have been hardly enough to be completely sure of the final choice.
The role of Merlin was the most difficult to cast, according to co-creator and executive producer Johnny Capps. He said: “We had to find an actor who has a broad playing range, someone with the lightness of touch who will be able to deal with action and magic. There’s a lot of green-screen work. We were looking for all of those qualities or the potential of those qualities, and the other important thing for Merlin was likeability. If the audience didn’t like Merlin then we might as well go home. We had an instinct about Colin. At first we weren’t sure about him but then saw him again and again and we watched back his final auditions and said, ‘He’s perfect for the part.’
It has been mentioned a few times that Colin received the pages for Arthur’s role and, once that was discovered, had to prepare very quickly to read for Merlin, that was his first reading. On one of the commentaries or bonus discs of the Merlin series … and I don’t remember which one … Colin and one of the producers were discussing someone being called back for further readings. Capps/Murphy said to Colin, “you were called back a number of times” and Colin responded, “yeah”. Then Capps/Murphy said, “I think it was about 10 times.” And the discussion ended there. Colin is not one to linger on his praises.
On another commentary, well into the second season, the director, Alice Troughton, remarked that Colin prefers not to be praised. She said this as recognizing his natural reticence to be singled out. That same trait of humility has remained with him throughout the roles that followed.