Red robot

A red robot was sent to Earth to find the heir to the throne of its planet. Along with a yellow robot, it removed all the humans, apart from those that were "grounded" by the Judoon, from Earth while they searched. The heir, a half-human called Gavin, was hidden by a biodamper. When the biodamper was removed, the robots recognised him. At his order, they returned the humans and took Gavin home. (TV: The Empty Planet)