Ben Jackson (Michael Craze)
Ben was fiercely loyal, protective and resourceful. He met the Doctor at the Inferno night club, shortly after receiving a six month shore posting.
Ben had also befriended Polly, the secretary of Professor Brett, who has been developing a malevolent computer, WOTAN. The Doctor accidentally took off with Ben and Polly on board, leading them to a series of adventures, including the Doctor's first encounter with the Cybermen.
Ben and Polly were present when the Doctor regenerated for the first time. When their travels eventually returned them to Earth, Ben and Polly took the opportunity to leave the Doctor.