Ned Leech

 was Brad Travers' superior officer at Alcatraz. He was a sadistic man, disliked by the guards and prisoners alike.

At some point, he was taken over by a Threckon, which used Leech's position to incite the prisoners to riot so that the Threckon could feed off their anger. When the Threckon confronted the Seventh Doctor, Leech was killed. (PROSE: Inmate 280)