Sally Jacobs

Sally Jacobs was a secretary working for the UNIT and members of staff underneath the Tower of London. Because of her blood group, A positive, she was controlled by the alien Sycorax and walked to the top of the tower to await her sudden death. After The Doctor foiled the Sycorax's plans, Sally returned to her original state, along with everyone else who was controlled. (DW: The Christmas Invasion)