Morrissey joined the cast of "The Walking Dead" for its third season in 2012. He portrayed The Governor, a major villain from the graphic novel upon which the series is based. Morrissey read the prequel novel "" to gain insight into the character and his motivations. He also worked with an accent coach and listened to politicians with Southern accents, including Bill Clinton. He returned for the fourth season in 2013, and made a cameo appearance in 2015. In 2014, Morrissey returned to British television in the David Nicholls drama "The 7.39" and the three-part serial "The Driver", written by Danny Brocklehurst.