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Speaking to the Los Angeles Times, Hamm suggested that Don's downward spiral in the fourth season proves that he has a heart.
"I think you have to be a psychopath to be able to tell that many lies and not have it affect you," he said. "And I don't think Don's a psychopath. I don't think Don's evil."
Hamm also admitted that playing such a dark side to Don was a challenge but explained that he understands him now.
"It was a reckoning," he said. "There were a lot of challenging things to play, but again this is the fourth season that I've played this guy, so there is a familiarity there with the character."
Mad Men continues in the UK on Wednesdays at 10pm on BBC Four.
