Joseph Fiennes, Claire Forlani, Jamie Campbell Bower

There's plenty of sword play and sex scenes in Starz' upcoming take on the legendary story of Camelot. But star Jamie Campbell Bower says those expecting "a beefy King Arthur" should keep looking.

"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 said during the Television Critics Association's winter preview sessions.

That attitude worked out well for the 22-year-old actor, who had to keep his small and pale physique intact for his day job as Caius, vampire leader of the Volturi in the Twilight saga. Bower, who said he was forced to do a month-long boot camp before shooting began on Camelot, said he felt it was important to show the progression from boy to man — a story similar to that of Starz' other successful historical drama, Spartacus.

"There was always this idea that he was a boy and he would grow and grow," Bower said. "At the beginning, I very much wanted [Arthur] to stay fleshy."

The young Arthur will still see plenty of action judging by the trailer screened for critics, which included racy love scenes, medieval battles and dark magic.

"We've approached it as a drama for adults," executive producer Chris Chibnall said. "There is some sex in there. There is some violence in there. It's its own beast. It's not really a family show. "

Starz will offer a sneak preview of Camelot on Feb. 25. The series will officially premiere in April.