Deborah Castle

 (nee Gordon), also known as Debbie, was a teacher in the 20th century.

Biography
Deborah once taught Miranda Dawkins and played a role keeping her safe from Ferran. She was also briefly the eighth Doctor's companion. She spent several days in transit with him across the globe so that they could together steal the Atlantis. Having done so, they were then able to rescue Miranda, who was in a spaceship in Earth orbit. Though a stowaway, Castle was nevertheless one of the few Britons to fly on an American spacecraft. (EDA: Father Time)