Cecil was a rogue Kaftakkrofakian who became a travelling salesman on Earth.
In the 1960s, he came to Earth with other Kaftakkrofakians looking to invade. Their attempts failed, and all of them left except Cecil. Stranded on Earth, he became a travelling salesman and fell in love with Bunty Hamilton. In 1979, the pair attended a party at the Ringroad Motel, where Cecil poisoned the food with an alien slime. When the guests ate the food, they became zombies, but the slime got into the electrics and set them on fire, burning down the motel. The Tenth Doctor persuaded Cecil to give him the antidote and took Cecil back to Kaftakkrofakia with Bunty. He was arrested and charged for his crimes and Bunty left him. (PROSE: Zombie Motel)