Speaking at the Television Critics Association tour, Campbell Bower explained that he did not want Arthur to be fully mature at the start of the series.
According to TV Guide, he said: "We find this character when he's in his late teens. What I didn't want to have was this aloofness and beefiness to him because people should be able to see that he's a boy and he has to grow into this man."
Bower added: "There was always this idea that he was a boy and he would grow and grow. At the beginning, I very much wanted [Arthur] to stay fleshy."
Starz will air a sneak preview of Camelot on February 25 and the series will officially premiere in April. The show will air on Channel 4 in the UK.