The actor, who will reprise the role that he first played in 2007's 'Utopia' in the upcoming end-of-year episodes, said that he was influenced by the Joker from the Batman series.
He told the Daily Mail: "If you thought I was hamming it up in the last one, wait till you see this. I like to be quite subtle, but this doesn't call for subtle. The Master is insane.
"I also used a bit of Caligula and a bit of Tony Blair. But in this, The Master is off the leash. Unhinged. Totally unplugged!"
He added of taking the role: "It was so I could prove to [my son that] daddy is an actor. He can never watch anything I'm in and this was perfect because he loves Doctor Who.
"There are moments I'll cherish for ever. The best bits about being a screen actor are the moments when the camera is behind you and, as far as the eye can see, you are in that world.
"There were also moments which were pure Boys' Own fantasy, but I can't say what because I don't want to ruin people's Christmas!"
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