The actor told The TV Addict that his character Arthur will be "very much at the helm" of Camelot in future episodes.
"[His father] Uther's kind of sat in the corner, screaming to himself and people aren't as ready to take orders from a madman," explained James. "Arthur has found himself in that position where he's having to take responsibility for the kingdom."
James also admitted that he is looking forward to the reunion between Arthur and Morgana (Katie McGrath), after the latter's wicked intentions were revealed at the end of series three.
"That [relationship] could go in any direction," he hinted. "For Arthur, you could probably ask the question, 'Does he still have that soft sport for her?', or has he just instantly turned and become anti-Morgana?"
Katie McGrath recently compared the newly-evil Morgana to Star Wars villain Darth Vader.
The fourth series of Merlin is currently filming in Wales and France, while a fifth run has already been commissioned.
> Merlin season four picked up by Syfy in US
Watch Anthony Head (Uther) discuss Merlin with Digital Spy below: