Created by David S. Goyer, the show transports viewers to 15th century Florence and introduces them to the dashing, brilliant Leonardo Da Vinci.
Asked how essential it was for him to demonstrate the larger-than-life figure's humanity, Riley told United Press International in a recent telephone interview, "It was the most important thing."
"There was no way on Earth I was going to have the mind of Leonardo Da Vinci, no matter how many encyclopedias I read, or how many text books I went through. So, the only way in was to connect to the more human elements of him," the 32-year-old actor explained.
"I remember reading a biography called 'Flights of the Mind' about him that said very clearly at the end, one of the final things in his notebooks said, 'I have to go to the kitchen because my soup is getting cold.' And I just thought, here among all this incredible stuff, he was just a man. We look back and mythologize him, but he also was the guy who worried about the temperature of his dinner."
Riley, who previously starred in the popular miniseries "Lost in Austen," as well as episodes of "Marple," "Poirot," "Freezing" and "Monroe," and the stage productions of "Arcadia" and "The Vertical Hour," said the part of Da Vinci was so great he just assumed he would go to a better-known actor. In a way, he insisted, the belief he wouldn't be cast as the lead in "Da Vinci's Demons" took some pressure off him during the audition.
"It was a giant opportunity and I went into it feeling like I had nothing to lose and so I pushed it in various directions," he said.
David S. Goyer, the show's creator, said he saw hundreds of actors before deciding Riley was perfect for the part.
"If David knew instantly [I was right for the role,] he didn't make that clear. I had no idea," Riley laughed. "He kept making me do it different ways. Now he wants [a take] where Da Vinci is very, very charming. Now he wants one where he is tormented. And, so, I guess I gave him the full spectrum of what he had in mind."
So, what was it like playing a man who walked the fine line of genius and madness?
"Oh, brilliant! I also have to say, as the season continues, we push him to a place where he's closer to madness than sanity," Riley said. "It's an incredible challenge. It's a gift. They come along once in a blue moon, that kind of part."
In addition to affording him the opportunity to play such a fascinating, well-developed character, Riley said the job also gave him the welcome chance to collaborate again with his good friend and "Lost in Austen" co-star Elliot Cowan.
This time around, Cowan plays Lorenzo Medici, Da Vinci's patron. Cowan played Mr. Darcy to Riley's George Wickham in "Lost in Austen," a small-screen re-imagining of Jane Austen's "Pride and Prejudice." Their "Austen" co-star Hugh Bonneville also has a cameo in the pilot episode of "Demons."
"I have such affection for 'Lost in Austen!'" Riley exclaimed. "I met some of my best friends on that job. We live really near each other and hang out all the time. Elliott is one of them, so it was really nice to go back and play completely different roles."
Co-starring Laura Haddock, Lara Pulver and Blake Ritson, "Da Vinci's Demons" is to premiere Friday night on Starz. Goyer wrote the 8-part series, served as showrunner and directed the first two episodes. The screenwriter of the upcoming Superman movie "Man of Steel" also has worked on the big-screen, comic-book adaptations "The Crow: City of Angels," "Blade," "Blade II," "Blade: Trinity," "Batman Begins," "The Dark Knight," "Ghost Rider: Spirit of Vengeance" and "The Dark Knight Rises."